Srikant2h

Contents

List of Figures

A STUDY ON THE FEEBLE DYNAMICS OF LEAD ZIRCONATE TITANATE 2013

INTRODUCTION Most of the technological applications of piezoelectricity used nowadays are based on ferroelectric materials. This is due to the following reasons: 1. Because of the high piezoelectric effect that can be found in these materials, a high and efficient electromechanical transformation of energy and signals can be achieved.

2. In general, the remnant electrical polarization that occurs in these materials can be oriented into a desired direction by applying an external electrical field: this means by poling, if needed, at elevated temperature. Therefore it becomes possible to imprint a unipolar direction of macroscopic preference or anisotropy to a device even after processing it. Obviously, this unipolarity is mandatory for every piezoelectric action.

3. Therefore, materials those are macroscopically isotropic by nature after the production process can be also used. This concern, e.g., ceramics, plastics, or composites, which can be processed using well-known methods to adapt and shape the material according to the requirements of the final use.

4. For piezoelectric applications, the group of ceramics based on the so-called perovskite structure is especially important. These materials are already being used over a broad field of technological applications such as capacitors and PTC resistors. Therefore, experience in the mass production, reliability, etc. of these materials is already available.

5. Therefore, also from the point of view of production cost, ferroelectric materials offer good advantages.

Consequently, it makes sense to offer here a short introduction into this class of materials.

Today, the most important piezoelectric materials that are technologically important are ferroelectric ceramics based on Pb-containing perovskites. They offer the advantages of most ceramic materials such as ease of fabrication, possibility of variable and application-adapted shaping, as well as low-cost manufacturing. In addition, diverse chemical modifications are available in order to tailor the piezoelectric properties to different applications. The preMTech. Nanoscience and Tech.

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condition, however, is the possibility to impose a unipolar anisotropy into the otherwise macroscopically isotropic ceramic. This is possible only if the spontaneous polarization can be oriented by a poling process using an external electric field for generating a remnant polarization. In addition, the special behaviour in the vicinity of ferroelectric phase transitions promotes extremely high piezoelectric effects, where the intrinsic ones are connected with the dielectric anisotropy and the extrinsic ones with increased domain wall mobility. Especially, in the periphery of the morphotropic phase boundary (MPB) present in a series of Pb-containing perovskites, such as lead-zirconate-titanate (PZT), this effect technically can be used extensively because the MPB in the temperature-composition phase diagram is nearly vertical, what implies nearly temperature independence.[16]. Piezoelectric ceramics PbZr,TiO3 PZT play an important role in electronic devices owing to their excellent electromechanical properties near the morphotropic phase boundary[16a]. It is known that the MPB plays a very important role in PZT ceramics because the piezoelectric and dielectric properties show a maximum over a specific com- positional range around the MPB [16b].

Definition of Ferroelectrics and Antiferroelectrics

A ferroelectric crystal is defined as a crystal which belongs to the pyroelectric family (i.e. e. shows a spontaneous electric polarization) and whose direction of spontaneous polarization can be reversed by an electric field. An antiferroelectric crystal is defined as a crystal whose structure can be considered as being composed of two sub lattices, polarized spontaneously in antiparallel directions and in which, a ferroelectric phase can be induced by applying an electric field. Experimentally, the reversal of the spontaneous polarization in ferroelectrics is observed as a single hysteresis loop (Fig. 3a), and the induced phase transition in antiferroelectrics as a double hysteresis loop (Fig. 3b), when a low-frequency ac field of a suitable strength is applied.

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Figure : Ferroelectricity is the phenomena of transition of cubic structures from Cubic to Tetragonal to Rhobohedral.

The spontaneous polarization in ferroelectrics and the sub lattice polarizations in antiferroelectrics are analogous to their magnetic counterparts. As described above, however, these polarizations are a necessary but not sufficient condition for ferroelectricity or antiferroelectricity. In other words, ferroelectricity and antiferroelectricity are concepts based not only upon the crystal structure, but also upon the dielectric behaviour of the crystal. It is a common dielectric characteristic of ferroelectrics and antiferroelectrics that, in a certain temperature range, the dielectric polarization is observed to be a two-valued function of the electric field [3]

Figure : Ferroelectric hysteresis Figure : Antiferroelectric hysteresis loop; Ps Spontaneous polarization,Pr loop. Ecrit, critical field Remnant polarization, Ec coercive field

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To be considered as ferroelectric, a material must satisfy two conditions [4]. First, it has to be a piezoelectric with two or more stable polarization states in the absence of an electric field.

Second, it must be possible to switch from one to another of these states by applying a sufficiently large electric field (nevertheless smaller than the breakdown field).

Ferroelectricity, first discovered in the Rochelle salt by Valasek [5], has been reported in different families of compounds, including hydrogen bonded systems such as KDP (potassium di-hydrogen phosphate; KH2PO4), polymeric systems such as PVDF (poly-vinylidene fluoride; [-CH2-CF2-]n), or the wide family of ABO 3 compounds. If selected first-principles calculations have been reported recently on KDP [6, 7] and PVDF [8], the great majority of the theoretical works concern the ABO3 family (mainly cubic perovskites but also trigonal [9] and hexagonal phases [10, 11]).

Figure : Classification of ferroelectrics and ionic crystal structure

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Figure : Comparison of domain wall structures in ferromagnetic and ferroelectric It is known that the domain wall (or boundary of two region in which the directions of spontaneous polarization are different from each other) of typical ferroelectric material is as thin as the order of a few lattices. The domain states in single-crystal freestanding isolated nanodots of PZT revealed that resultant polarization structures were found to consist of largescale closed loops in polarization, very similar to the flux-closure patterns already known in ferromagnets, but scarcely observed in ferroelectrics [3].

Ferroelectrics exhibit a spontaneous electric polarization that can be reversed by an applied electric field, in the same way that a ferromagnet’s spontaneous magnetic moment can be reversed by a magnetic field [12].

Engineering of Ferroelectric Phase Transitions The extreme which occur in the dielectric, pyroelectric, elasto-electric and opto-electric properties of ferroelectrics at temperatures close to the phase transitions take the properties into exceedingly interesting and practically important ranges. It is thus important to explore the mechanisms which can be used to modify and control the transition behaviour. In the perovskite system, five types of control are important •

For solid solutions, the phase transition temperatures often change continuously with composition so that in homogeneous compositions the transitions may be placed at optimum temperatures. Further, by controlling a deliberate heterogeneity a range of transitions can be engendered spreading and smoothing the sharp extreme

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•

In some solid solutions, ferroelectric: ferroelectric phase transitions occur at fixed compositions and are nearly independent of temperature. These so called morphotropic phase boundaries are extremely important in piezoelectric ceramics.

•

Elastic stress can have a marked effect on the transition behaviour and the property extreme near the transition so that self-generated stresses in ceramics may be engineered to improve the properties.

•

For ceramic compositions the grain: grain boundary heterogeneity can be invoked to modify extreme and to control the field distribution in the ceramic.

•

Since ferroelectricity is a cooperative phenomenon the scale of the ferroelectric region is of critical importance. Nano-scale heterogeneity can engender completely new properties and give rise to spin glass behaviour which

can be exploited in both

capacitors and transduces [13].

Today, the most important piezoelectric materials that are technologically important are ferroelectric ceramics based on Pb-containing perovskites. They offer the advantages of most ceramic materials such as ease of fabrication, possibility of variable and application-adapted shaping, as well as low-cost manufacturing. In addition, diverse chemical modifications are available in order to tailor the piezoelectric properties to different applications. The precondition, however, is the possibility to impose a unipolar anisotropy into the otherwise macroscopically isotropic ceramic. This is possible only if a poling process using an external electric field for generating a remnant polarization can orient the spontaneous polarization. In addition, the special behaviour near ferroelectric phase transitions promotes extremely high piezoelectric effects, where the intrinsic ones are connected with the dielectric anisotropy and the extrinsic ones with increased domain wall mobility. Especially, in the periphery of the morphotropic phase boundary (MPB) present in a series of Pb-containing perovskites, such as lead-zirconate-titanate (PZT), this effect technically can be used extensively because the MPB in the temperature-composition phase diagram is nearly vertical, what implies nearly temperature independence [14]

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The development of ferroelectric bulk materials is still under extensive investigation, as new and challenging issues are growing in relation to their widespread applications. Progress in understanding the fundamental aspects requires adequate technological tools. This would enable controlling and tuning the material properties as well as fully exploiting them into the scale production. Apart from the growing number of new compositions, interest in the first ferroelectrics like BaTiO3 or PZT materials is far from dropping. The need to find new leadfree materials, with as high performance as PZT ceramics, is pushing towards a full exploitation of barium-based compositions. However, lead-based materials remain the best performing at reasonably low production costs. Therefore, the main trends are towards nanosize effects and miniaturization, multifunctional materials, integration, and enhancement of the processing ability in powder synthesis. Also, in control of dispersion and packing, to let densification occur in milder conditions [15]

Piezo electricity In 1880, the French physicists Pierre and Jacques Curie discovered that mechanical pressure on the surface of certain crystals (e.g. PZT, lead-zirconate-titanate) generates electrical charges.

They called this phenomenon the piezo effect. “Piezo” originates from the Greek and means both “pressure” or “press”. An electrical charge can be measured on two crystal surfaces while the pressure changes (bending, stretching, and pressing) which is proportional to the force expended. The stretching is extremely minimal – ultimately a crystal cannot be pressed together like a sponge.

Figure : Behaviour of ferroelectrics with the illustration of charge development over and below the crystal and method of extraction of charges.

The illustrations provide a greatly simplified presentation of the functions of the piezo effect.

The first image shows a rendering of a six-sided crystal structure cell. All charges are mutually equalized so that the cell has a neutral electrical effect from the outside in. The pressure on this MTech. Nanoscience and Tech.

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structural cell (image in centre) causes a shift of the centres of gravity of the positive and negative charges against each other. The resulting difference in the charge is evaluated as voltage or a charge (right image).

Figure : The hysteresis, Curie temperature, electrical and mechanical energy generation from the other form.

Working of piezoelectric materials Mechanical compression or tension on a poled piezoelectric ceramic element changes the dipole moment, creating a voltage. Compression along the direction of polarization, or tension perpendicular to the direction of polarization, generates voltage of the same polarity as the poling voltage. Tension along the direction of polarization, or compression perpendicular to the direction of polarization, generates a voltage with polarity opposite that of the poling voltage.

These actions are generator actions, where by the ceramic element converts the mechanical energy of compression or tension into electrical energy. If a voltage of the same polarity as the poling voltage is applied to a ceramic element, in the direction of the poling voltage, the element will lengthen and its diameter will become smaller. If a voltage of polarity opposite that of the poling voltage is applied, the element will become shorter and broader. If an alternating voltage is applied, the element will lengthen and shorten cyclically, at the frequency MTech. Nanoscience and Tech.

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of the applied voltage. This is motor action, where by electrical energy is converted into mechanical energy. The principle is adapted to piezoelectric motors, sound or ultrasound generating devices, and many other products. And it’s this phenomenon which is exploited for energy, or voltage generation during various experiments that the piezoelectric materials are subjected to.

Figure : Direct and indirect effect of piezoelectric material showing voltage generation when compressed and shape change when voltage is applied.

Direct piezoelectric effect: D-Charge density d=deffX

deff-effective piezoelectric coefficient

Converse piezoelectric effect

X-stress

X=deffE

x-strain

Electrostrictive effect-quadratic effect,present for all materials Xij=QijPkPl Material Property: piezoelectric coefficient (third-rank tensor, dijk ) di=dijkXjk For particular case of tetragonal symmetry: d33=2ε33Q33P3 d31=2ε33Q13P3 d15=2ε11Q44P3 MTech. Nanoscience and Tech.

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Figure : Tensor map of all the different vectors in many dimensional spaces Relation between piezoelectric co-efficient and polarization: dim=εikQmikPk

ε-dielectric permittivity m-index in the matrix notion

For polycrystalline materials sample parameters on sample symmetry:

Figures of merit: X=dE E=gX

g=d/ε

d-actuating figure of merit g-sensor figure of merit

Electromechanical coupling factor k k2=Stored mechanical (electrical ) energy / stored electrical (mechanical) energy k2=d2/(εs)

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Phase Diagram

Figure : Maximum d in systems with morphotropic phase boundary (MPB) The significant feature of this phase diagram is the morphotropic phase boundary (MPB) at a composition where the PZ: PT ratio is almost 1 : 1. At an MPB there is an abrupt change in the structure with composition at a constant temperature. These structural relationships can be explained more clearly, using the ferroelectric (and piezoelectric) solid solution system of Pb (ZrxTi1-x)O3 (lead zirconate titanate, PZT). The two end members are PbTiO3 that undergoes at 490째C a simple phase transition from a paraelectric cubic to a ferroelectric tetragonal phase, and PbZrO 3 that behaves in a more complex fashion, having a transition from cubic to an antiferroelectric orthorhombic phase.

Replacement of Zr by Ti produces low-and high-temperature rhombohedral ferroelectric phases. Below the Curie temperature, the phase field of the ferroelectric states is separated by a near-vertical line, the morphotropic phase boundary (MPB).

Observations from Figure on monoclinic phases at MPB are that a. Not a sharp boundary between tetragonal and rhombohedral phases exists b. An additional monoclinic phase might exist c. There are three different phases with similar free energies and

the

polarization

can

rotate

easily

among

different

directions[16] Figure : Monoclinic phase at MPB MTech. Nanoscience and Tech.

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Interpretation of the piezoresponse signal Piezoelectric

coefficient

for

single-crystal

mono-domain

ferroelectrics

with

a

centrosymmetric paraelectric phase are given by the parametric relationships: d33=2ε33Q33Ps3 d31=2ε33Q13Ps3 d33=2ε33Q33Ps3 For other cases effective values may apply dzz=2εzzQzzPsz

Figure : Randomly oriented grains-polycrystalline films and formation of alignment under polarization.

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PZT Surfaces

Figure :Piezoelectric surface for PZT

Figure : Effect of orientation on We can comment on the effect of various hysteresis. Note that dzz is not proportional to Pz parameters from the figure above.

Fundamentally speaking, role of hysteresis is important in understanding how the domains orient. The orientation of domains has a strong correlation with the piezoelectricity generated from the ceramic.

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The last decades have seen a rapid evolution in the atomistic modelling of materials, driven both by the fast and recurrent increase of the computational power (hardware), and by important progresses in the development of more efficient algorithms (software). Nowadays, it is possible to describe very accurately the properties of materials using methods directly based on the fundamental laws of quantum mechanics and electrostatics. Even if the study of complex systems requires some practical approximations, these methods are free of empirically adjustable parameters. For this reason, they are referred to as “first-principles� or "ab-initio" techniques. Since 1990, ferroelectric oxides have been intensively studied from first-principles, and significant advances in the microscopic understanding of their properties have been achieved.

Figure : Ferroelectric nanowires

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Figure : Piezoelectric nanoshell tubes

Figure : Figures of merit for large area hydrophones which can be developed using various composite geometries [17] The last decades have seen a rapid evolution in the atomistic modelling of materials, driven both by the fast and recurrent increase of the computational power (hardware), and by MTech. Nanoscience and Tech.

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important progresses in the development of more efficient algorithms (software). Nowadays, it is possible to describe very accurately the properties of materials using methods directly based on the fundamental laws of quantum mechanics and electrostatics. Even if the study of complex systems requires some practical approximations, these methods are free of empirically adjustable parameters. For this reason, they are referred to as “first-principles� or "ab-initio" techniques. Since 1990, ferroelectric oxides have been intensively studied from first-principles, and significant advances in the microscopic understanding of their properties have been achieved [18]

About Electromechanical Systems Automatic control system is a system of feedback and actuation with input and output. No system can be automatic unless these feedback elements are included. A system that is dynamic in real world is never a standalone entity of any single area of application. Its parameters occupy another state of inertia only when there are some forms of energy expenditure. Thus a state variable gets defined in space. Hence control system is an essential feature of all autonomous working entity and it comprises of electronics, electrical, mechanical drives and feedback systems to enable adaptive filtering. The practice of workshop is an inseparable part of constructions involving actuating parts [19].

The machine elements of electrical practices [20] had to be amalgamated in our work with mechanical parts [21]. Hence this discussion is relevant.

Gear: A gear is a toothed member. It is designed to transmit motion and thus power to another toothed member by successively engaging its teeth with those of the other gear. The teeth may be cut on cylindrical or conical or rectangular or elliptical blocks. The tooth shape and sizes of gears are standardized.

Bearing: A bearing is a machine element which supports another moving machine element and guides its motion. In general a bearing supports a shaft which is rotating either in a horizontal plane or in a vertical plane. The portion of the shaft which is in actual contact with the bearing surface is called the journal. During the process, the bearing carries the load and prevents the motion of the shaft in the direction of the applied load. The bearings are located between the contact members and the linkage members or frame of a machine.

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Pulley: Pulleys are used to transmit power from one shaft to the other at a moderate distance away by means of a belt or strap running over them. They may be of cast iron, wrought iron, pressed steel or wood. Main shaft pulleys are generally made of wrought iron, pressed steel or wood which gives them suitable strength combined with lightness, while countershaft pulleys which are usually smaller than main shaft pulleys are made of cast iron. These pulleys have a thin rim of rectangular section over which the belt runs. Usually, pulleys are provided with arms which maybe straight or curved and the cross-section is usually described as “oval”, i.e., roughly elliptical. The central part of the pulley is called the “nave”, “eye” or “boss”. To add strength and stiffness large pulleys are provided with ribs between the rim and the boss.

Sometimes these ribs are reinforced with arms for greater stiffness and durability. The rims of all cast iron pulleys are generally “crowned”, i.e. slightly greater in diameter at the center than at the edges. As the belt seeks the highest point on the pulley, the effect of crowning is to keep the belt in a central position. The crowning of pulleys, in most cases, should not exceed 25 mm on the diameter per meter of width, and the width of the pulley should be one-fourth greater than the width of the belt used. The minimum diameter of pulleys should be at least 24 times the thickness of belt used.

Shaft: It may be said that the shaft is the essential element for transmitting power in mills and workshops. Under operation, a shaft is subjected to combined torsion and bearing. An axle is a stationary shaft on which pulleys and other members rotate. An axle sometimes rotates, but is subjected to bearing only. The part of the shaft within the bearing is known as journal.

Journals at the ends of the shaft (or axle) are called pivots, while the intermediate journal is a neck journal. A spindle is a machine shaft that drives and supports either a cutting tool or the work on which machining and other operations are performed.

Wire rope: When a large amount of power is to be transmitted over long distances from one pulley to another (i.e. when the pulleys are up to 150 metres apart), then wire ropes are used.

The wire ropes are widely used in elevators, mine hoists, cranes, conveyors, hauling devices and suspension bridges. The wire ropes run on grooved pulleys but they rest on the bottom of the grooves and are not wedged between the sides of the grooves. The wire ropes are made from cold drawn wires in order to have increase in strength and durability. It may be noted that the strength of the wire rope increases as its size decreases. The various materials used for wire ropes in order of increasing strength are wrought iron, cast steel, extra strong cast steel, plough steel and alloy steel. For certain purposes, the wire ropes may also be made of copper, bronze, aluminium alloys and stainless steels.

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Spring: A spring is defined as an elastic body, whose function is to distort when loaded and to recover its original shape when the load is removed. The various important applications of springs are as follows: 1. To cushion, absorb or control energy due to either shock or vibration as in car springs, railway buffers, air-craft landing gears, shock absorbers and vibration dampers.

2. To apply forces, as in brakes, clutches and spring loaded valves.

3. To control motion by maintaining contact between two elements as in cams and followers.

4. To measure forces, as in spring balances and engine indicators.

5. To store energy, as in watches, toys, etc.

Sensors: A sensor is a device that converts a physical phenomenon into an electrical signal. As such, sensors represent part of the interface between the physical world and the world of electrical devices, such as computers. The other part of this interface is represented by actuators, which convert electrical signals into physical phenomena.

Figure : Stepper Motor Motor: An electromechanical energy conversion device makes it possible to convert energy from electrical to mechanical or from mechanical to electrical form. Thus, this device can be considered an electromechanical transducer. The device, which converts mechanical energy into electrical form, is a generator, while the device, called motor, converts electrical energy to mechanical form. The conversion process is reversible and hence generators can be made to act as motors.

Stepper motor: Stepper motors are essentially incremental motion devices. The input to the motor is train of pulses and output is an angular rotation of its shaft by a certain number of degrees as dictated by the number of pulses in the train of pulses. A microcomputer or an electronic circuit is used to control the train of pulses. As a result, a stepper motor is very much compatible with digital electronic circuits. So, it may be used as an interface between a MTech. Nanoscience and Tech.

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microcomputer and a mechanical system. Since the rotation of the stepper motor is controlled by the number of pulses, no feedback loop or sensor is needed for its control. Hence, stepper motors are suitable for position control in an open loop system. These motors are relatively inexpensive and simple in construction. These motors can be made to rotate in steps in equal increments in either direction. Hence, a stepper motor can position an object accurately on an input command in the form of a number of pulses. For this reason, stepper motors are used in printers, X-Y recorders, electric typewriters, control of floppy disk drives, robots and numerical control of machine tools. Some of the drawbacks of stepper motor are that they do not offer the flexibility of adjusting the step size and the step response may be oscillatory in nature with a considerable overshoot. These motors can be grouped into three broad classes, namely variable reluctance type, permanent magnet type and hybrid type.

Transformer: In a circuit when a mutual inductance exists, the inductance is actually associated with the magnetic field linking with a circuit. With the existence of a mutual inductance between two circuits, a magnetic coupling becomes established. The coupling between the two circuits permits the energy transfer between the two circuits. This is the concept utilized in the construction of an electric transformer.

Figure : Transformer **********

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LITERATURE SURVEY Methods of PZT Formation Thin films of lead titano-zirconate (PZT) were prepared in-situ using radio-frequency sputterdeposition. Then in-situ perovskite formation is very sensitive to the substrate temperature (Ts) and the sputtered lead flux; the incident lead flux is controlled by the lead content in the target (X). Perovskite phase can be obtained under a relatively wide range of (X; Ts) combinations.

The lower growth temperature is 5101C associated to X=1.10 and the optimized growth temperature, in terms of optical and electric properties, is Ts=5501 (X=1.50). At this temperature, the relative dielectric constant is equal to 860 and the dielectric losses are in the order of 0.019. The remnant polarization and the coercive field are, respectively, 19 mC/cm 2 and 42 kV/cm. The piezoelectric coefficient e 31 is maximum without poling treatment; it is in the order of 5.2 C/m2 PZT films were prepared in-situ on platinized silicon substrates by reactive sputtering. The control of Pb content in the film is obtained under a wide range of X and Ts combinations. The in-situ growth mechanism was governed by the degree of Pb species re-evaporation from the film during the growth; a competition exists between the reevaporation/incorporation of PbO and the formation of PZT [22].

Lead zirconate titanate (PZT) thick films were formed on several kinds of substrates by impact consolidation of PZT ultrafine particles through an aerosol deposition method. The primary PZT powder in use is commercially available raw-powder material (PZT-LQ: niobium modified PZT; Sakai Chemical Ind.), which is dry-milled to improve the deposition rate. This powder has a perovskite structure and a composition of Pb (Zr 0.52 ,Ti0.48)O3 , which is close to the morphotropic phase boundary. High-density PZT thick films deposited on several kinds of substrates by the aerosol deposition method (ADM) were shown to have a high breakdown voltage––about 700 kV/cm––after an-nealing at temperatures from RT to 10001 C. As a result, this layer after annealing and poling demonstrated good piezoelectric properties as -d31 ~100pm/V and good fatigue properties, which were comparable with those of PZT thin films deposited by conventional methods. These findings suggest a good deal of potential for piezoelectric actuators [23].

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Crack free Pb Zrx Ti1-x O3(x=0.45) films with various thicknesses were prepared by a sol-gel multiple coating process on Pt-coated Si 100 substrates. Rapid thermal annealing RTA methods were used to crystallize the amorphous PZT films. The sol-gel deposition route is of immense interest for applications of thin film capacitors due to their compatibility to photolithography, their low temperature processing, large area coating ability, precise composition controlling and low cost. There are primarily three chemical solution approaches to depositing lead perovskite dielectrics: 2- methoxy ethanal 2-MOE -based, the acetic acid-based and recently developed 1, 3-propanediol-based. Well-densified PZT films have been obtained, and the interface between the layers is homogeneous [24] Lead zirconate titanate (PZT) compositions near morphotropic phase boundary (MPB) Pb (Zr x Ti1−x)O3, 0.48≤x≤0.54, were prepared by wet chemical route using water soluble precursors.

Compositions were prepared with donor dopants, such as La3+ ,Nd3+ or their combinations. The combined hydrous precursors were calcined in the temperature range of 750–900 ◦C. PZT powders with MPB compositions as well as with donor dopants were prepared by wet chemical route. Between lanthanum and neodymium, lanthanum produces better piezoelectric and polarization properties than neodymium for the same concentration of dopant [25].

Bernal et al. reported a bottom-up nanomanufacturing

method for fabrication of

piezoelectrically-active, ferroelectric PbZr0.52 Ti0.48O3 (PZT) nanotubes with aspect ratios up to 5:1, based on vacuum infiltration of the precursor sol-gel solution into a polymeric template, created using electron beam lithography (EBL). This method allows fabrication of ferroelectric nanostructures with user-defined shapes, location, and pattern variation across the same substrate enabling fabrication of NEMS devices based on ferroelectric smart materials [26].

Using a torque-rheometer, ceramic-polymer extrudable mixtures were prepared to produce lead zirconate titanate (PZT) fibres through a co-extrusion process. For the preparation of the piezoelectric fibres, a commercial PZT powder (PZT/SKN, Ceram Tec AG), a fugitive material (carbon black BP ® 120, Cabot Corporation) and a thermoplastic binder system containing low density polyethylene (LDPE, PEBD-1700 MN 18C, Lacqtene, Elf Atochem S.A.) and stearic acid (Fluka AG) were used. The rheological behaviour of a lead zirconate titanate containing feedstock (58 vol. % of filler) and a carbon black/polyethylene mixture (35 vol. % of filler), capable for a co-extrusion shaping process, was analyzed using a torque-rheometer. Coextruded PZT fibres were successfully achieved after de-binding and sintering monofilament composites processed at similar flow behaviour conditions of the feedstock. Although coMTech. Nanoscience and Tech.

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extruded fibres showed similar microstructure properties and only a slightly higher porosity than the extruded ones, the electromechanical performance was noticeably inferior [27].

Nanocrystalline lead zirconate titanate PZT powders were prepared starting from the solution of Ti IV , Zr IV , Pb II ions complexed with organic acids and amines. The complex solutions after complete evaporation decomposed and produced fluffy masses, which after calcination at lower temperature in comparison to solid-state method yield the desired phase of PZT. Various complexing agents such as oxalic acid, tartaric acid, ethylene di-amine tetra acetic acid (EDTA), di-ethanolamine (DEA) have been used to influence the particle size and dielectric property in the PZT system. Nanocrystalline PZT powders have been prepared from the thermal decomposition of metal-complex precursors at relatively lower heat treatment temperature compared to that of the solid-state method. The use of DEA or tartaric acid in the system provided a homogeneous distribution of metal ions preventing their precipitation or segregation from the solution during the dehydration process. After complete dehydration, the exothermic decomposition of metal complexes produced sufficient heat, for nanophase formation. Thus, the PZT phase formation occurs at relatively low external temperature in the DEA and tartarate-based methods, in comparison to other reported methods except hydrothermal method [28].

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Table : Preparative methods for fine PZT powders (R N Das et al.)

Low temperature synthesis process involves a redox-type exothermic reaction in which the nitrate ions of the precursor act as oxidizing agent and the hydroxyl groups of ethylene glycol as a reducing agent. PZT formation takes place at a low temperature of 5000C [29]

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Table : Average particle sizes of from three syntheses of R N Das et al.

Epitaxial Pb(Zr0.52Ti0.48)O3(PZT) thin film has been successfully integrated on Si(001) substrate by sol-gel method. SrTiO3(STO) layer deposited on Si by Molecular Beam Epitaxy (MBE) acts as a template layer in this study to avoid the formation of amorphous SiO 2, and allows the chemical compatibility for further epitaxial growth. Epitaxial PZT thin film was successfully achieved by sol-gel deposition on STO-buffered Si(001) substrate. SRO layer grown by PLD was suitable as bottom electrode due to the epitaxial structure and low resistivity. The quality of STO template strongly influences the properties of PZT film by introducing defects and domain walls [30] High quality PZT films were deposited by RF magnetron sputtering onto 200 mm thermally oxidized silicon substrates at substrate holder temperatures (Th) between 550°C – 700°C using PbO-enriched single ceramic PZT targets. The high substrate temperatures used here allowed direct growth of the piezoelectric perovskite phase and rendered an additional post annealing step unnecessary. The Pb/(Zr+Ti) atomic ratio exhibited a monotonic decrease with increasing Th, with the morphotropic phase boundary stoichiometric values Pb/(Zr+Ti) ~ 1 and Zr/ (Zr+Ti) ~ 0.53 obtained at 700°C [31].

Lead-based ferroelectric thin films, PT and PZT, have been deposited on platinized silicon substrates by using rf magnetron sputtering technique. Whatever the deposition network, the MTech. Nanoscience and Tech.

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piezoelectric

character has been demonstrated for all films. The piezoelectric

response

dependence of the poling treatment with the time and the applied dc electric field has been studied. Ferroelectric thin films such as perovskite structure compounds PbTiO 3 (PT), Pb(Zr, Ti)O3 (PZT) and (Pb, La) (Zr, Ti)O3 (PLZT) are considered to be promising for applications in microelectronics using their polarization reversal, high-dielectric-constant characteristics and their piezoelectric activity. The poling behaviour was determined by measuring the piezoelectric activity as a function of poling field and poling time [32].

Ferroelectric PZT thin films were prepared on Pt/Ti/SiO 2 /Si substrates by using a sol–gel method. The PZT films were annealed in air at 650 °C for 30 min. The thickness of films was between 1500 and 4500 Å [33].

Wetting of the pore walls of porous templates is a simple and convenient method to prepare nanotubes. Ferroelectric lead zirconate titanate and barium titanate nanotubes were fabricated by wetting of porous silicon templates of polymeric precursors. The ferro- and piezoelectric properties of an individual ferroelectric either of a PZT or a BaTiO 3 nanotube were electrically characterized by measuring the local piezoelectric hysteresis. One-dimensional structures such as nanotubes or nanorods from many materials have attracted great interest in the last decade, because they exhibit different physical properties than their bulk counterparts. Fer-roelectric oxides are an important class of functional materials for research and for applications since they exhibit interesting properties such as spontaneous polarization, high dielectric permittivity as well as piezo- and pyro-electric effects [34] PZT (70/30) thick films were fabricated by the screen-printing method on alumina substrates and PZT (30/70) precursor solution with the different composition ratio, which prepared by sol-gel method of Pb-acetate trihydrate, Zr n-propoxide and Ti isopropoxide, which were dissolved in 2-methoxyetnanol. The PZT powders are kneaded with 30 wt% of organic vehicle (Ferro B75001) to obtain screen-printed pastes. The Pt bottom electrodes were screen-printed on the alumina substrate. The PZT pastes were screen-printed on the platinised substrate and were dried at 400 ◦C for 20 min. The printing and drying procedure was repeated four times.

These PZT thick films were sintered at 1050 ◦C for 2 h in PbO atmosphere. And the PZT (30/70) precursor solution with the tetragonal structure was prepared by sol-gel method. The PZT (30/70) precursor solution was spin-coated on the PZT(70/30) thick film using a spinner operated at 2000 rpm for 30 sec. These PZT films dried at 300 ◦C for 30 min to remove the organic materials., was spin-coated on the thick films [35] MTech. Nanoscience and Tech.

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In order to search for ferroelectricity in soft biological tissues, Y. Liu et al. carried out piezoresponse force microscopy (PFM) studies on porcine aortic walls. Tissue samples were dried prior to PFM analysis; the aortic wall consists of three layers of intima, media, and adventitia. Piezoresponse force microscopy (PFM) is a powerful tool to probe electromechanical coupling in piezoelectric and

ferroelectric systems at nanoscale.

Ferroelectricity in soft biological tissues, however, has not been observed in this study. Using PFM, Liu at al. showed that porcine aortic wall is not only piezoelectric, but also ferroelectric with a modest coercive voltage. In addition, the polarization switched by a negative voltage is not stable, and will reverse spontaneously to a more stable orientation shortly after removal of the negative voltage, suggesting that the polarization in aortic wall is internally biased outward [36] The physical nature of the PZT powders, i.e. particle size, distribution and shape are determined by their processing techniques. One of the most widely used processing methods for fabrication of PZT is a solid-state mixed-oxide technique because of its simplicity and cost effectiveness. Among these methods, sol-gel processing is one of the most interesting chemical processing techniques for fabrication of PZT powder because of its considerable advantages in producing powder with high purity and uniformity at molecular level in addition to low operating temperature requirement. These give rise to the ceramics with good compositional and structural homogeneity which often justifies the need for using expensive and moisture sensitive alkoxide compounds as starting materials. The raw materials used were PbO (99%, Fluka), TiO2(99%, Fluka) and ZrO2(99%, Fluka) powders. The mixture was ball milled, dried and calcined at 800 ◦C for 2h to form a ball-milled PZT powder. The PZT sol was prepared using a triol sol-gel route. The starting materials were zirconium (IV) propoxide (70 wt% in 1propanol, Aldrich) and acetylacetone (99%, Fluka). Under a dry nitrogen atmosphere, the mixture was refluxed in an oil bath at 90 ◦C for 2 h, cooled down to room temperature before addition of titanium (IV) isopropoxide (99%, Aldrich), lead (II) acetate trihydrate (99.99%, Aldrich) and 1,1,1-tris (hydroxymethyl) ethane (99%, Aldrich). The mixture was then heated at 70 ◦C for 4 h. The final product was a viscous golden sol. After that, the PZT ball-milled powder (30 wt%) was added into the sol (70 wt%), vigorously stirred, dried and calcined at 600 ◦C for 4 h. This sol-bonded PZT powder was then pressed into pellets at 100 MPa and sintered in a PbZrO3-powder atmosphere at 950–1200 ◦C for 4 h. The results obtained in the study suggested that a large number of the smaller sol-gel particles could be used to fill the

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interstice between large particles of ball milled particles, which resulted in an improved densification[37] An approach to synthesize lead zirconate titanate (PZT) powders with a modified two stage mixed oxide synthetic route has been developed. To ensure a single-phase perovskite formation, an intermediate phase of lead zirconate (PbZrO 3) was employed as starting precursor. The formation of perovskite phase in the calcined powders has been investigated as a function of calcination temperature. It has been found that the perovskite PbZrO 3 and PbTiO3 phases tend to form together with PZT, with the latter appearing in both tetragonal and rhombohedral phases, depending on calcination temperatures [38].

High temperature annealing of sol-gel derived PZT may cause cracking and diffusion of structure layers. The introduction of a buffer layer, (La xSr1-x)MnO3, between PZT thin film and metal electrodes improves PZT crystallization and ferroelectricity [39].

The liquid source misted chemical deposition (LSMCD) method was employed in the preparation of lead zirconate titanate, Pb (Zr0.52Ti0.48)O3 (PZT) thin films. The desired thickness of the films was adjusted by a number of successive deposition/heating cycles. Typically, a 500-nm-thick film was achieved by running four processing cycles. The PZT films showed good phase purity with a (111)-preferred crystallographic orientation [40].

The films were fabricated using a VacTek planar dc magnetron sputtering system with a post-deposition rapid thermal annealing treatment at 650 0C for 10 s. The thermal conductivity of silicon is higher than that of quartz, ITO, and PZT, and silicon absorbs most of the incident radiation with wavelength less than 1 μm whereas quartz, ITO, and PZT are transparent in that energy region. [41] 0.025Nb-0.0125Sr-PZT ceramics was prepared by mechanical milling of Pb3O4,TiO2,ZrO2, SrCO3 and Nb2O5 (all reactants were reagent grade). The powder mixture was calcined at temperature of 900 ◦C for 1 hour and calcinate was mechanically activated by wet or dry milling in planetary ball mill (Fritsch, Pulversiette 7) using the ZrO 2 milling elements (vessel and balls) at various milling times. The activated calcinate was pressed into pellets form and sintered at 1150 and 1200 ◦C for 1 hour in air. In final ceramic samples, both the microstructure and dielectric properties (at 1, 10 and 100 kHz) were studied. Ceramics prepared from 20 and 30 minutes wet milled calcinates (sintering at 1200 ◦C) had microstructures with coarse grains (average grain size approximately 6 µm) in comparison with the microstructure of the sample MTech. Nanoscience and Tech.

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prepared from non-milled calcinate (NMC) (avg. grain size of 3 Âľm). Densities of all ceramic samples were similar to each other and they were very close to value of 96% of theoretical density [42].

Ordinary bananas exhibit closed loops of switched charge versus applied voltage that are nearly identical to those misinterpreted as ferroelectric hysteresis loops in crystals. The `ferroelectric' properties of bananas are contrasted with those of the real ferroelectric material Ba2NaNb5O15, often nicknamed `bananas' [43].

Kim et al. recently succeeded in synthesizing various oxide nanostructures including PZT nanowires by a template-directed growth in conjunction with sol-gel process and a spin coating technique (TSS method) for obtaining physical properties such as finite size effects or unusual phase transitions, for a wide range of potential applications to nanoscale piezoelectric actuators, force sensors, ultrasonic transducers, and non-volatile memory devices [44].

Influencing Factors Usually, bulk PZT exhibits the highest piezoelectric coefficient d 33 or e31 at the morphotropic phase boundary (MPB), around 53% Zr. In that case, domains of both tetragonal and rhombohedric symmetry contribute to a high piezoelectric response. Thin film applications usually based on the effective transverse piezoelectric coefficient e 31,f. The maximum of the piezoelectric coefficient seems to be in the tetragonal region of the phase diagram [45].

A Michelson interferometer was used to measure the thickness strains due to an applied ac electric field. Effective d33 piezoelectric strain coefficients were computed from the experimental data. Interfacial pinning caused these coefficients to differ from the true ones.

They were corrected for the pinning using both an analytical model and finite-element analysis.

The corrected coefficients of the PZT (52/48) sample were in excellent agreement with values of bulk materials. The coefficients of the multilayer sample were very low, probably due to insufficient poling or domain switching [46].

The PZT films with a composition near the morphotropic phase boundary were epitaxially grown on (100) Pt-coated MgO substrates by RF-magnetron sputtering. The PZT films exhibited excellent ferroelectricity with a remnant polarization more than 50 mC/cm2 . In order to examine intrinsic piezoelectric properties, cantilever structures were micro fabricated with the PZT films. The piezoelectric coefficient d 31 of PZT films, which were not subjected to MTech. Nanoscience and Tech.

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poling treatments, was measured directly from the transverse expansion of the cantilever beams. The measurements revealed that the PZT films were naturally polarized and had a relatively large piezoelectric coefficient d31 of 100x10-12 m/V without poling. Piezoelectric resonances were clearly observed for the PZT cantilevers by the measurement of admittance [47].

Study on various process parameters have led to the following conclusions: i) Lead excess in the initial powder has the tendency to segregate and evaporate creating pores; ii) The grain size and the granulometry distribution of the initial powder have a strong effect on the porosity by improving the green density of the PZT layers.

These effects are more pronounced in thick films in comparison to bulk ceramics; iii) The loading of powder in the inks enables to improve the densification of thick layers but a control of the rheology of the ink is also necessary to avoid a too high plasticity threshold [48] Electromechanical properties of (1-x) Pb (Mg1/3Nb2/ 3)O3-xPbTiO3(PMN-PT) single crystals with x=0.35 were investigated as a function of different external disturbances. The polarization dependence on the electromechanical properties was first studied in order to determine the best polarization path. Temperature, stress, electric field and time (aging) stability was studied in order

to

determine

performance

limiting

factors

of

these

materials.

The

rhombohedral/tetragonal phase transition is observed on temperature (80 0C), inducing a decrease of the electromechanical coupling factor (from 85% to 50%); but the whole properties are recovered while returning to room temperature. Stress measurement shows a large depoling of sample for stresses above 30 MPa. The PMN-PT single crystals were found to be surprisingly stable during aging, except for mechanical and dielectric losses. The same tendency was found on alternating current (AC) electric field dependence [49].

Hydrothermal Methods The term advanced material is referred to a chemical substance whether organic or inorganic or mixed in composition possessing desired physical and chemical properties. In the current context the term materials processing is used in a very broad sense to cover all sets of MTech. Nanoscience and Tech.

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technologies and processes for a wide range of industrial sectors. Obviously, it refers to the preparation of materials with a desired application potential. There are several methods of processing advanced materials like physical vapour deposition, colloidal chemistry approach, mechanical

milling,

hydrothermal,

mechanical

biomimetic,

flame

alloying

techniques,

pyrolysis,

laser

sol-gel,

ablation,

mechanical ultrasound

grinding, techniques,

electrodeposition process, plasma synthesis techniques, microwave techniques, other precipitation processes, etc. Among these processes, the hydrothermal technique contributes to around 6%. However, it has been realized that the hydrothermal technique facilitates the fabrication of even the toughest or the most complex material(s) with a desired physicochemical properties. Normal hydrothermal solution routes is a recent concept to describe a set of processes in a broader sense covering conventional hydrothermal (with aqueous solvent in the system), solvothermal (with non-aqueous solvent in the system) and supercritical hydrothermal (either aqueous or non-aqueous under super-critical conditions) processes. The term hydrothermal is purely of geological origin. It was first used by the British geologist Sir Roderick Murchison (1792-1871) to describe the action of water at elevated temperature and pressure, in bringing about changes in the earth’s crust leading to the formation of various rocks and minerals. It is well known that the largest single crystal formed in nature (beryl crystal of >1000 kg) and some of the largest quantity of single crystals created by man in one experimental run (quartz crystal of several 1000s kg) are both of hydrothermal origin.

Hydrothermal processing can be defined as any homogeneous (nanoparticles) or heterogeneous (bulk materials) reaction in the presence of aqueous solvents or mineralizers under high pressure and temperature conditions to dissolve and recrystallize (recover) materials that are relatively insoluble under ordinary conditions. Byrappa and Yoshimura (2001) define hydrothermal as any homogeneous or heterogeneous chemical reaction in the presence of a solvent (whether aqueous or non-aqueous) above the room temperature and at pressure greater than 1 atm in a closed system. Here the authors have defined the term hydrothermal in a traditional and broader sense covering conventional hydrothermal, solvothermal, and supercritical hydrothermal, solvothermal hydrothermal processes.

Among various technologies, available today in advanced materials processing, the hydrothermal technique occupies a unique place owing to its advantages over conventional technologies. It covers processes like hydrothermal synthesis, hydrothermal crystal growth leading the crystal growth of fine to ultra-fine and nano crystals, bulk single crystals, hydrothermal

transformation,

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sintering,

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hydrothermal stabilization of structure, hydrothermal dehydration, hydrothermal extraction, hydrothermal treatment, hydrothermal phase equilibrium, hydrothermal electrochemical reactions, hydrothermal recycling, hydrothermal microwave supported reaction, hydrothermal mechano-chemical, hydrothermal sonochemical, hydrothermal electrochemical processes, hydrothermal fabrication, hot pressing, hydrothermal metal reduction, hydrothermal leaching, hydrothermal corrosion and so on. The hydrothermal processing of advanced materials has lot of advantages and can be used to give high product purity and homogeneity , crystal symmetry, metastable compounds with unique properties, narrow particle size distribution, a lowering sintering temperature, a wide range of chemical compositions, single-step processes, dense sintered powders, submicron to nano-particles with a narrow size distribution using simple equipment, lower energy requirements, fast reaction times, lowest residence time, as well as for the growth of crystals with polymorphic modifications, the growth of crystals with low to ultralow solubility, and a host of other applications. Since then the knowledge on the physical chemistry, PVY relationship in the hydrothermal systems greatly improved, which helped in drastically reducing the temperature and pressure conditions of processing. Similarly, the solvothermal and supercritical processing which used a variety of other solvents like organic, organometallic complexes in materials processing, thereby taking technology towards Green Chemistry [50].

The hydrothermal synthesis of lead zirconate titanate (PZT) powder with acicular morphology using organic mineralizer, tetra methyl ammonium hydroxide penta hydrate (TMAH), has been investigated. Perovskite lead zirconate titanate (PZT) powder with cubic and acicular morphology has been prepared directly from aqueous solution by hydrothermal synthesis using TMAH as a mineralizer. The phase composition and morphology of PZT particles synthesized in the hydrothermal process depend on the TMAH concentration. At lower TMAH concentration (0.5 m< TMAH <0.75 m), the acicular shape of the intermediate particles is preserved during the hydrothermal reaction due to in situ transformation, resulting in the PZT powder with acicular morphology. The hydrothermal synthesis of lead zirconate titanate (PZT) powder with acicular morphology using organic mineralizer, tetra methyl ammonium hydroxide penta hydrate (TMAH), has been investigated. Depending on the TMAH concentration, the intermediate either dissolves to form cube-shaped PZT (TMAH concentrations of 1â&#x20AC;&#x201C;4 m) or transforms in situ to acicular PZT powder using its fibrous morphology as a template (TMAH concentrations of 0.5â&#x20AC;&#x201C;0.75 m) [51]

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To some degree EDTA complexation plays a role in suppressing perovskite formation, owing to its high thermodynamic stability. Lead EDTA complexation does not completely suppress lead titanate formation. Use of Pb/Ti ratio equal to 2 does not lead to precipitation of an undesirable phase such as PbO. This is due to the complexing action of EDTA with lead species that are in excess with respect to the titanium species [52].

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Hydrothermal synthesis is accomplished by the use of suspensions or homogeneous solutions subjected to temperature and pressure to induce rapid phase transformation kinetics. This synthesis method falls under the category of wet chemical methods that includes sol-gel and co-precipitation. The wet chemical routes achieve purer and finer powders than the conventional solid-state calcination route. Unlike other wet chemical methods, the hydrothermal method can be used to prepare anhydrous phase-pure oxides in a single step synthesis route from inexpensive precursors. During the process, no hazardous volatiles are produced. Furthermore, the water-based solvent can be recycled. When a stress is applied, the dipoles align in one direction to provide a polarization that is called the piezoelectric effect.

The ferroelectric state is when the crystals contain a spontaneous reversible electric dipole moment. The paraelectric state is when the dipoles in neighbouring cells are randomly oriented relative to each other. The change from paraelectric to ferroelectric state occurs at the Curie temperature and corresponds to the change in dielectric constant. Therefore, many perovskite materials are used for applications in electronics (e.g., non-volatile memories, transducers, actuators, and capacitors) based on their special electronic properties.

Flaschen [55] in 1955 was the first to publish an article written about the hydrothermal synthesis of the ferroelectric materials. The synthesis conditions (e.g., pH, temperature, and concentration) as well as the purity of the precursor materials significantly affect the chemical and phase purity of the resultant powders. The optimal approach to control the chemical phases of the ferroelectric perovskite under equilibrium conditions is to calculate the stability and yield conditions of the perovskite by a thermodynamic model. The results of the calculation of the model are the equilibrium concentrations of all species as a function of pH, temperature, and initial reagent concentrations. Reactions without the additive of EDTA would have produced a yield diagram with PbO precipitate.

Urek et al. [54] found that TMAH requires a burnout step at 800Ë&#x161;C before the sintering of a ceramic material. If additives are used during the hydrothermal reaction, the reaction could be hindered. For example, Kiss et al. [56] found that Cynamer P-250 and Elvanol 50-42 prevented the complete reaction of BaTiO3. Another variable in the final product is the homogeneity of the starting precursor. An unavoidable contaminant of the hydrothermal process is the hydroxyl groups that attach to the lattice of the crystal structure and adsorb on the surface. Without the appropriate length of time, the reaction will not be complete even with the correct synthesis conditions (i.e., pH, temperature, initial reagent concentration). Furthermore, the reaction time will also contribute to the resulting powder morphology and size of the product.

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Two main mechanisms or a combination of these mechanisms in rate determining for the hydrothermal reaction of ferroelectric powders are: dissolution-precipitation and in-situ transformation. A dissolution-precipitation mechanism occurs when soluble reactants are heated over time. When there is sufficient dissolution of the ions, supersaturation is achieved and the product is formed. An in-situ transformation mechanism assumes a surface (topochemical) reaction of cations (i.e., Ba) with a less soluble species (i.e., TiO 2) in water. The reaction proceeds by the diffusion of cations through the structure of insoluble species until the completion of the reaction. Once the condition of supersaturation of critical nuclei is obtained, precipitation may occur. The supersaturation is the metastable state of a solution in which soluble species remain in solution even though their thermodynamic equilibrium limit is exceeded. The particle size and morphology is also dependent on the supersaturation and the growth mechanism. This can be affected by initial precursor, ratio of precursors, temperature, time, additives, mineralizer type, and mineralizer concentration. Under the mechanism of nucleation and growth, the particle size is expected to decrease with an increase in supersaturation. However, in the presence of slightly soluble species, particle size is expected

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to increase with an increase in pH (mineralizer concentration) and an increase in reaction time.

Figure : Illustration of mechanisms of PZT formation in hydrothermal technique However, if the reaction proceeds by a diffusion-limited mechanism, the starting size of the precursor should be the main contribution to the final particle size. Concentration can affect the particle size. The molar ratio of the precursors can affect the particle size. The mineralizer type or additives of organic materials may stabilize smaller particles by the steric effect. The concentration of mineralizer affects the particle size. The particle size of the hydrothermally prepared perovskite was found to increase as a function of time. The crystallite size is affected by temperature. The process of precipitation includes an initial induction time due to the creation of supersaturation, primary and secondary nucleation, and growth stages [53].

When trying to synthesise PLZT powders Traianidis et al. observed that lanthanum, instead being integrated within the PZT network, forms needles by reacting separately with lead MTech. Nanoscience and Tech.

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precursor. At first, it is necessary to determine the mechanism of PZT crystallisation in hydrothermal conditions, and whether a homogeneous PZT solid solution can be formed starting from a heterogeneous precursor system. This second condition must be satisfied if oxide precursors have to be used. Traianidis et al. developed a new synthesis route based on a 2-stage process. The first stage consists in treating amorphous zirconia and crystalline titania with a KOH initial concentration sufficiently high to attack titania and form the KTO phase.

Dopants, like lanthanum can be integrated in the network at this step. After the treatment, the mixture is washed until the achievement of a neutral medium. After the addition of lead precursor, a second hydrothermal treatment is performed [57a].

During the hydrothermal treatment, the spherical gel powders retained their spherical shape, incorporating sources of A-site ions, and the resulting powders were crystallized to produce spherical perovskite oxide powders, composed of nanometre-sized particulates. Because the reaction elements (Ti and Zr) were confined within the spherical gel powders, limiting the growth space of the crystalline perovskite, it is supposed that the synthesized perovskite powders retained their spherical shape and were composed of fine particulates [57b].

Yttrium-doped zirconia, lead zirconate titanate (PZT) and barium titanate were successfully obtained using hydrothermal procedures. Based on these results mathematical models describing the correlation between the nanopowdersâ&#x20AC;&#x2122; characteristics and the main synthesis parameters are proposed. The activation energy shows that the process kinetic is diffusioncontrolled. Controlling the grain size in the nanometre range significantly improved the ionic conductivity. A factorial experiment was done to determine the mathematical equations that represent the objective function variation with the process parameters. Thus the crystallization degree and crystallite sizes of the powders can be estimated and calculated to obtain powders with the desired molar composition. Crystallite sizes influence powders processing parameters and have an important impact on the electrical characteristics [58].

Vertically aligned nanowires and highly uniform nanoporous array thin films of PbTiO 3 are synthesized by varying anodic oxidation conditions of Ti foil followed by hydrothermal reaction in an aqueous Pb (II) acetate trihydrate solution. The first step of the synthesis was anodic oxidation of Ti foil to obtain titanium oxide nanostructures. The second step was the hydrothermal reaction to convert the anatase TiO2 into PbTiO3. The nanotubes were transformed to single crystalline nanowire PbTiO3 structure, whereas nanoporous film turned to polycrystalline nanoporous PbTiO3 , both with pure tetragonal phase [59].

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Phase-pure perovskite lead titanate and lead zirconate titanate with various morphologies have been synthesized by hydrothermal methods at 150 and 175 0C, respectively. Solution pH should be greater than 14 to obtain the phase-pure perovskite phases in a reasonable time. In addition, the KOH concentration and the stirring rate significantly influence particle morphology of the hydrothermally derived PT and PZT. Therefore, these parameters can be used to tailor particle size and morphology [60].

PZT films obtained from a hydrothermal method were first reported by Shimomura et al [61].

S. Euphrasie et al. present another hydrothermal treatment using titanium substrates and mineral precursors leading to a “gel” enabling the growth of our PZT films. In the “crystal growth” process, some TiCl4 is used as titanium precursor, the temperature is lower (120 ◦C instead of 150 ◦C) and KOH concentration is halved [62].

Compositional Concentration The PZT films were obtained by RF magnetron sputtering of a PbZr0.54Ti0.46O3 target containing additional PbO in an amount of 10 mol %.All the thin-film capacitor structures studied initially had a spontaneous polarization vector oriented toward the lower electrode, which was indicative of an impurity conductivity of the electron type. The degree of unipolarity varied within 1.5 times from one contact pad to another, which might be indicative of an inhomogeneous distribution of PbO over the film surface. Thus, an excess of lead oxide in PZT films accounts both for their unipolarity and for a strong asymmetry of the pyroelectric hysteresis curves. Orientation of the spontaneous polarization vector is indicative of the electron conductivity in such films. A high degree of unipolarity can be observed in the films of practically important compositions near the morphotropic phase boundary, where both piezoelectric and pyroelectric coefficients reach their maximum possible values [63].

To compensate lead losses during high temperature annealing in the crystallization process of CSD PZT films some additional quantity of the lead are added as a rule in initial solution. The formation of PtxPb intermediate phase is considered as a possible way promoting nucleation of (111) perovskite phase while PbO appearance at the interface stimulates creation of (100) PZT texture. The platinum layer plays a role of a substrate on which PZT grains are nucleated.

Grain boundaries of perovskite grains are also decorated by PbO inclusions having extended form (pointed by arrows). The film is strongly textured in {111} direction, all grains grow through the whole thickness of the film, and it contains less pyrochlore inclusions. This leads MTech. Nanoscience and Tech.

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to a symmetric hysteresis loop, low coercive voltage and high capacity. In contrast to case mentioned above, the annealing temperature does not have significant influence on the film structure and properties. Perovskite grains are not growing therewith through the whole thickness of a film [64].

Composition analysis and profiling was performed on a PZT prepared from reactive magnetron sputtering by means of X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering (RBS). RBS data was recalibrated to exclude hydrogen content not determined by XPS [65].

The PbO content of lead zirconate titanate (PZT) films has been widely recognized as affecting not only the phase assembly and microstructure but also the dielectric and ferroelectric properties. Excess PbO has often been incorporated in PbO-based films to optimize the film properties by compensating for PbO loss either through volatilization or, diffusion into the substrates. Sol-gel derived PZT 53/47 films with various PbO contents, i.e., Pb x Zr0.53 Ti0.4703 (x = 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.05, 1.10, 1.25 and 1.5) were prepared on platinized Si wafers and fired to temperatures ranging from 55OC to 7OOC under oxygen. Multiple spin coating with an intermediate firing of 4OOC between coatings was performed to obtain films up to 0.5 pm thick. After the final crystallization firing, top Pt electrodes were sputtered to form monolithic capacitors. These capacitors were subjected to dielectric and ferroelectric characterization using an impedance analyser and a Radiant Technologies RT66A Ferroelectric Test System.

PZT films which are highly deficient in PbO (i.e., x < 0.8) tend to crack due to diffusion into glass substrate during annealing when they are thicker than 5000A. For these films, the precursor solution concentration was adjusted to obtain films of about 3000A thick. The values of G and dissipation factor increase with increasing PbO content due to the abundance of perovskite phase compared to pyrochlore phase. Films fired to 600C containing only the pyrochlore phase exhibited low values of G (< 200) and dissipation factor due to the paraelectric nature of the pyrochlore phase. Excess PbO seems to promote the formation of the perovskite phase. The appearance of the ferroelectric perovskite phase, which contributes to the overall polarizability leads to an increase in the dielectric properties. Once again, the presence of perovskite phase and its relative content with respect to pyrochlore are responsible for the FE behaviour. In amorphous or single- phase pyrochlore films, no hysteresis loop was observed due to the absence of any switchable FE component. Generally, the polarization and coercive field increased and decreased respectively, denoting the higher relative amount of perovskite phase compared to pyrochlore, with increasing PbO content. Pyrochlore films are paraelectric MTech. Nanoscience and Tech.

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and do not exhibit any FE behaviour. With increasing PbO content, the perovskite phase tended to dominate over pyrochlore and the films became more non-linear dielectric, leading to higher values of εr , dissipation factor and P, but lower E c’s. Excess PbO also lowered the perovskite crystallization temperature, aiding in its formation during film firing [66].

Single-phase PLSZT thin films were deposited on platinised silicon and fused quartz substrates by sol gel technique. Both the cation substitutions are being substituted at A site only. The thin films were grown on Pt/Si<111>substrates by sol gel technique. XRD diffractogram shows single phase for the films for x=0.02. Thereafter, an unidentified phase starts appearing which increases with further substitution of Sm3+ . Surface morphology was studied using atomic force microscope (AFM). The films show well-defined ferroelectric behaviour. The dielectric constant decreases with Sm substitution initially and then increases slowly as the Sm substitution is increased but never attains the pure PLZT (8/65/35) dielectric value. The loss tangent (tanδ) initially increases and then decreases. The phase transition temperature (Tc) increases drastically with 2 mol% Sm substitution and decreases slightly as the Sm substitution is increased further. The I-V behaviour shows a consistent shift towards the negative bias voltage as the Sm substitution is increased from 2 mol% to 8 mol%. The logI-logV curve show ohmic behaviour with the electrode for all the samples. The P-E loop shows more hysteresis for the 2 mol% Sm substitution. The appearance of P-E loop qualitatively shows the piezoelectric nature of the films. Optical band gap was calculated from transmittance studies using a UV-VisNIR spectrophotometer. The optical band gap was estimated from (αhυ) 2 vs. hυ curve. The band gap decreases first with Sm substitution and then increases as the Sm substitution is increased [67].

After experimenting with electric field and stresses on Fe-doped PZT, it was concluded by J. Suchanicz et al. that applying uniaxial pressure induces similar effects as increasing the Ti ion concentration in PZT system. The obtained results were interpreted through Cochran soft mode and domain switching processes under applying of pressure [115]. The same conclusion was reported elsewhere for PLZT 9/65/35 [125].

Poling A shear mode plate-shaped lead zirconate titanate (PZT) actuator for a novel actuating module in a micro droplet ejecting system was fabricated and tested. A novel poling design with both poling electrodes on the same surface is proposed by C H Cheng et al. The actuator is made MTech. Nanoscience and Tech.

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with lateral polarization parallel to the plane, in contrast to the conventional actuator with the polarization along the plate-thickness direction. Due to the requirement for the excellent electromechanical coupling characteristics, the samples poled under various poling conditions were tested and compared to determine the optimum conditions. The poling conditions, including the poling voltage, poling temperature and poling duration, affect the electromechanical characteristic or output actuated displacement. The distribution of electric field in the sample during poling was simulated using commercial finite element method (FEM) software to predict the appropriate poling voltage. Experimental results indicate that the optimum conditions are a poling voltage of 7 kV, a poling temperature of 120 ◦C and a poling duration of 10 min. The sample with the optimum condition has the highest out-of-plane displacement of 400 nm under an actuating peak-to-peak voltage of 120 Vpp [68].

The nonlinearity of hard and soft PZT ceramics was studied before and after poling. The nonlinear phenomena are classical type before poling, with the amplitude of the second harmonic larger than that of the third harmonic. On the other hand, after poling, the nonlinear phenomena became the non-classical type with the amplitude of the third harmonic larger than that of the second harmonic. Such phenomena are more obvious in soft PZTs than in hard PZTs. Micro cracks induced by domain switching are thought to be responsible for such interesting nonlinear phenomena. The nonlinearities also change with time initially, but become stable two days after poling [69].

Within the lead zirconate–lead titanate (PbTiO3–PbZrO3) solid solution, the compositions with the highest piezoelectric coefficients are near or at 52% Zr and 48% Ti concentration (PZT 52/48), corresponding to the morphotropic phase boundary between Ti-rich tetragonal and Zrrich rhombohedral PZT. Thin PZT films are difficult to pole relative to bulk ceramics, as substrate clamping causes domain pinning, impairing polarization reversal. PZT films tend to be in tensile stress after fabrication as a result of thermal expansion, mismatch between film and substrate. Poling changes (100)-oriented domains within the crystals to (001)-oriented domains, causing the film to contract in-plane. Contraction of the film in-plane during poling increases the tensile stress still further, which is relieved by cracking of the thin film—this is clearly undesirable. The ease and completeness of poling are improved at higher temperatures since domain wall mobility is increased, improving domain alignment. Cracking increases conductivity, which reduces charge retention. Film stiffness is also reduced by cracking and this has a greater impact on e 31,f than d33,f. the fields required for direct-contact poling were MTech. Nanoscience and Tech.

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sufficiently strong enough to cause micro-cracking under the surface of the electrode, limiting domain switching and reducing the measured piezoelectric coefficients [70].

The depoling field of PZN-(6–7%)PT single crystal is about 0.3 kV/mm, which is much lower (nearly 6 times) than the overpoling field. The low depoling field of relaxor single crystals may be related to their comparatively low coercive fields of about 0.35 kV/mm. In designing actuators using this crystal cut, one should work with unipolar forward electric field and that the applied field must be kept below the overpoling field strength of the crystal. To this end, unimorph actuators are preferred to bimorph actuators when single crystal active elements are used. Furthermore, the single crystal should be placed under compression when possible. One should thus exercise care to ensure that the overpoling field of the crystal is not adversely affected by the applied compressive stress. The axial tensile stress in the [110] direction in this case will force the polarizations in the two affected domain variants to rotate toward the tensile stress direction (i.e., toward the [110] crystal direction), thereby increasing the polarization angle, θ (i.e., that made by the said polarization vectors with the applied electric field direction) in the process. Thus, at sufficiently high axial tensile stress, the polarization vectors concerned may be switched from the two affected [111] directions to the two opposite [110] crystal directions, corresponding to a transformation of the affected domain variants from the rhombohedral (r) state to the orthorhombic (o) state. This also brings about concurrent partial depolarization of the crystal, because only two of the four domain variants are affected in this crystal cut. When this occurs, an abrupt change in the capacitance of the single crystal is expected [71].

A few phase field simulations were carried out to explore the piezoelectric behaviour in the rhombohedral ferroelectric single crystal subjected to anisotropic poling. It has been found that poling in the [0 0 1] direction resulted in a reduced hysteresis loop. Due to mainly the effect of large shear piezoelectric coefficient d15, the longitudinal piezoelectric coefficient d33 in the nonpolar direction [0 0 1] was found to be much larger than that in the spontaneous polar direction [1 1 1]. Electric loading was applied along [0 0 1] and [1 1 1] directions separately. It was found that poling in the [0 0 1] direction resulted in a reduced hysteresis loop and an enhanced longitudinal piezoelectric coefficient. By changing the lead–zirconate–titanate (PZT) composition, a PZT with composition near the morphotropic phase boundary showed an extraordinarily large increment in the longitudinal piezoelectric coefficient [72].

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A shear mode PZT actuator for the micro droplet ejecting system is proposed. The plate-shaped actuator poled with remnant polarization perpendicular to the actuating field induces a piezoelectric shear effect. Two poling designs for the shear mode piezoelectric actuator are compared by both analysis and experiment. The two poling designs are the single-surface poling design and the dual-surface poling design. The single-surface poling design arranges the poling electrodes on only one surface, while the dual-surface poling design arranges the poling electrodes on opposite surfaces. Although the single-surface poling design is convenient for the poling process, its requirement for a higher poling voltage to achieve a coercive field induces specimen failure by surface cracking. So, the dual-surface poling design is preferred because a higher yield and better electromechanical coupling characteristic can be obtained. In both the poling designs, the relation of the shear piezoelectric coefficient,d 15, and the actuating electric field are obtained with three kinds of sample thickness [73].

The PZT was doped with 2 mol% neodymium and 1.1 mol% manganese. For characterization, the fibres were embedded in a polymer. The resulting 1â&#x20AC;&#x201C;3 composites were poled with constant electric field. Strain and polarization were measured by applying a bipolar sinusoidal voltage of high amplitude. Instead of the expected shifted butterfly-shaped strain hysteresis, an asymmetric strain-field relation was observed. It is characterized by a rather linear region in direction of the poling field and an inflated region without strain switching for reversed polarity. Within the temperature range from room temperature to 80°C, the strain switching seems to be suppressed. A measurement of the piezoelectric coefficient at superimposed electric field has proved the blocking of strain switching [74].

The essential ferroelectric property is the possibility of reversal, or change in orientation, of the polarization direction by an electric field. The hysteresis loop is a manifestation of this key property. Additionally, Ferroelectricity is characterized by a specific property: mechanical and electric loads of sufficient magnitude may change the dipole orientation of unit cells, leading to domain switching and domain wall motion. The key physical phenomena governing the nonlinear response of ferroelectrics below the Curie temperature is switching of the remnant electrical polarization of crystalline material between distinct polarization states. When the remnant polarization switches between distinct states, the switch is in some cases accompanied by a change of shape of the unit cell, giving rise to remnant strain. Consequently, switching may be driven by stress (termed ferroelastic switching) or by electric field. The poling process may differ from one substance to another. Mechanical stresses may play a role in the poling.

For instance, some perovskite ferroelectrics such as BaTiO3 , it is often straightforward to MTech. Nanoscience and Tech.

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obtain a single domain plate by application of electric field alone, while for others, such as PbTiO3 ,it is easier to remove a-axis type domain with an applied stress in the plane of the plate while orienting c-axis or 180o domains with a field. An alternative procedure for poling ferroelectrics is to switch reverse domains below the Curie temperature with electric fields higher than the Curie temperature with electric fields higher than the coercive field. For several materials high coercivity allows poling in this way only near to T c, but in most materials electrical poling may be achieved by cooling a crystal from the paraelectric phase into the ferroelectric phase in an applied electric field parallel to the polar crystallographic axis under constant condition of the electric field [75].

The poling behaviour of PZT (53/47) films was investigated separately at the grain boundaries and inside the grain volumes by ESFM. The films were prepared by sol-gel processing on Ptmetallized polycrystalline Al2O3,-substrates and consisted of columnar grains with mean diameter of 220 nm. It was found that the polarization was decreased at simple grain boundaries in a border zone of 20 nm to 40 nm width, with up to 42% related to the grain volumes. At triple points, the polarization was decreased by the same amount in a border zone of 40 nm to 80 nm width with respect to the grain volumes. An asymmetric poling behaviour of the saturation polarization was found at the grain boundaries. The switchable polarization is defined as the difference of positive and negative saturation states. The switchable polarization of the grain boundaries was determined to be 74% of that of the grain volumes. The coercive field was clearly increased at the grain boundaries [76].

It is found that the poling procedure is more effective when the film is exposed to a broadband UV light in the presence of a high electric field. Piezoelectric coefficients are increased and aging rates are decreased as compared to poling in dark conditions. Both an internal bias field and a polarization offset are observed in the piezoelectric hysteresis loops. The piezoelectric coefficients were increased and the aging rate was decreased as compared to poling under dark conditions. The mechanism of the photo induced poling effect in PZT films is probably due to electron trapping near the film-electrode interface. It is worthwhile to emphasize that in conventional polarization measurements only the internal bias field (or voltage offset) could be seen after the analogous poling procedure. The advantage of the piezoelectric technique is that the absolute value of polarization can be estimated since d33 is coupled to the polarization (P) via the general electrostriction equation: d33=QeffÎľ0ÎľP, MTech. Nanoscience and Tech.

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where Îľ0 is the permittivity of vacuum, Îľ is the dielectric constant, and Q eff is the effective electrostriction coefficient which only weakly depends on the external parameters [77].

Major structural changes occur in a piezoelectric material during the poling process. The original isotropic symmetry, due to the random orientation of the individual crystals, is broken and an induced polar axis appears. Then the elasto-piezo-dielectric matrix of poled ceramics becomes equal to that corresponding to the same material but with cylindrical symmetry. The whole set of physical parameters (the elements of the elasto-piezo-dielectric matrix) changes dramatically. Consequently, the isotropic original material (non-piezoelectric) is transformed into a piezoelectric one, with its elastic and dielectric properties closely linked. The most important change takes place in the piezoelectric constants and in the mechanical coupling factors, which increase from zero up to their saturation values. Nevertheless, it must be remarked that the mechanical strain produced in the material constitutes a strong boundary condition for its dielectric behaviour and, reciprocally, the internal electric field can be responsible for large mechanical stresses. The piezoelectric coupling factors show a clear increase. The maxima of the numerical derivative take place at lower poling field values than those corresponding to the piezoelectric parameters. This can be explained as due to the contribution of the elastic and dielectric constant to the coupling factors. All these facts indicate the existence of a narrow range of poling field values in this material for which piezoelectricity, as well as all structural changes related to it, is induced [78].

Subjected to the prior out-of-plane poling, the ferroelectrics can be toughened considerably.

Wei et al. describes the variation of the stress intensity factor (SIF) by 90 0 switching in ferroelectrics. The analysis is carried out for the combined mechanical and electrical loading, with simple relations obtained for the case of the purely electrical loading. The out-of-plane poling is found to raise the SIF for the crack initiation, but appreciably reduces the SIF for the crack growth in a steady state. More stable fracture resistance curves can be achieved by the out-of-plane poling. This prediction is supported quantitatively by the testing data of SENB specimens of PZT-5 samples, when the toughening effects of poling in three orthogonal directions are compared [79].

Takahiro et al. experimented with a specimen that was placed on a hand-made poling instrument and that was polarized using various conditions for each factor with a high voltage generator (Glassman Co., Ltd., WR100N2.5DMO) in silicone oil (Shin-Etsu Chemical Co., Ltd., KF-54) keeping the temperature constant. The ratio of voltage elevation was about 1 kV s MTech. Nanoscience and Tech.

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1

. After poling, the applied voltage was lowered to zero in the silicone oil, keeping the

temperature high. The charge was freed by short-circuiting both electrodes after cooling. The poling temperature, poling electric field, poling time and the distance between electrodes were chosen as the factors. Because Megacera, Inc. recommends 120 0C-60 min-3 MV m-1 as the standard poling condition, Takahiro et al. set that combination as the standard condition in this work. Piezoelectric materials are polarized more easily when the poling temperature is higher.

Therefore, we chose a higher temperature, shorter poling time and lower poling electric field.

TAKAHIRO et al. selected 2x10-3 m and 10x10-3 m as levels for the distance between electrodes [80] The two compared actuator structures were both based on commercial PZT 5H bulk discs with thicknesses of 375µm (Ø 25 mm), where one was machined into a graded structure with a steplike decrease of the thickness towards the centre and one intact. The poling conditions of the structurally graded actuator have to be more carefully selected compared to the case of the bulk actuator. The remnant polarisation values of the graded actuator were slightly lower than nongraded bulk values. The graded structured actuator obtained higher coercive field compared to the non-graded actuator. Remnant polarisation and coercive electric field values of the graded actuator depend more on the poling field than in the case of the bulk actuator [81].

The PZT-5 ceramics used in this investigation is a soft PZT near the morphotropic phase boundary, where the tetragonal phase and rhombohedral phase coexist. The parent blocks of PZT-5 ceramics, with the dimension of 18x10x56 mm 3 , were firstly poled along the 18 mm direction. The poling procedure was conducted above the Curie point. Then the parent block was cut into four individual blocks with the dimension of 10x10x14 mm 3 , whose long axes form different angles (0°, 30°, 60°, and 90°) to the poling direction [82] Empirical measurements of fracture toughness and fatigue strength were conducted for piezoelectric Pb (Zrx,Ti1−x)O3 of various compositions such as tetragonal, MPB, and rhombohedral. Before the poling treatment, the rhombohedral showed the highest fracture toughness, while the tetragonal revealed the lowest fracture toughness. After poling treatment, the fracture toughness measured by the pre-cracked SENB method decreased in all three compositions. The most remarkable decrease was observed in the tetragonal composition.

However, when the indentation strength method was used, the highest fracture toughness was observed in the tetragonal. The stress intensity factor relief due to micro cracks around the indentation marks and the anisotropic internal stresses caused by domain alignment during the MTech. Nanoscience and Tech.

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poling treatment were proposed as explanations for the conflicting results. The fracture toughness of tetragonal PZT in the unpoled condition was higher than that in the poled condition, and the higher fracture toughness in the unpoled condition was explained in terms of domain switching at the instant of fracture. Fatigue resistance was lowered by the compressive stress introduced during the poling treatment. The highest fatigue resistance was observed in the rhombohedral composition of low tetragonality, which exhibited low internal stress. These are the established facts from the experiment: 1. Before poling treatment, the highest fracture toughness measured by a single precracked SENB method was observed in the rhombohedral, while the tetragonal showed the lowest fracture toughness. Poling treatment decreased the fracture toughness of PZT in all three compositions. The most prominent decrease in fracture toughness was observed in the tetragonal composition, where the anisotropic internal stress introduced by the domain alignment was parallel to the electric field direction for poling.

2. The discrepancies in fracture toughness values depending on the different measurement methods were explained in terms of the concept of a single crack (in a precracked SENB method) and multiple cracks (in an indentation strength method). Anisotropic internal stresses from the tetragonality which were introduced during the poling treatment were used to explain the extent of the decrease in fracture toughness for the various crystal structures of PZT. 3. Unpoled PZT exhibited higher mechanical fatigue resistance than poled PZT in all three compositions. The highest fatigue resistance among the three compositions was observed in the rhombohedral composition; this was attributed to the lower anisotropy of stress distribution, higher density, and smaller grain size [83].

The poling procedure has always been the key issue in producing piezoelectric actuators with optimized performance. This is also true with the relatively new category of pre-stressed bender actuators, where mechanical bias achieved with a passive layer is introduced in the actuators during manufacturing. Due to these factors, the behaviour of the actuator under poling is different compared to its bulk counterparts. In this paper, two different thicknesses of commercial PZT 5A and PZT 5H materials were used in bulk actuators and pre-stressed benders realised by new method. Pre-stress was introduced by using a post-fired biasing layer utilising sintering shrinkage and difference in thermal expansion. The hysteresis loop of the actuators was measured under 0.5â&#x20AC;&#x201C;7.0 MV/m electric fields at 25â&#x20AC;&#x201C;125 â&#x2014;ŚC temperatures, providing information about their remnant polarisation and coercive field before poling. The MTech. Nanoscience and Tech.

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results showed that high electric field and 25 0C temperatures in poling provided higher remnant polarisation and coercive electric field than using 125 ◦C temperatures at poling.

Difference was especially significant in coercive electric field values where up to 114.8% difference was obtained for PZT 5H bulk actuator and 65.9% for pre-stressed actuators. Higher coercive fields can be utilized as increased operating voltage range of piezoelectric devices.

The differences in results obtained here and by others can be explained by the different prestress level, stronger clamping of the thicker passive layers of the RAINBOW and THUNDER actuators and passive ring area introducing high tensile stresses. The same conditions were used to pole the actuators, after which the displacement and dielectric constant of the actuators were measured. The displacement measurements showed that remnant polarisation has good correlation with displacement. This fact can be used in estimating pre-stressed actuator performance before actual poling. The dielectric constant measurements with a small signal after poling gave even better correlation than the remnant polarisation [84].

Ultra-fine PZT (∼40–50 nm) nanocrystals with pure perovskite tetragonal phase were synthesized by a hydrothermal method by W C Liu et al. To obtain the optimum electro-optic properties of poled composite films, the poling condition under an external electric field was optimized through the dielectric properties of PZT and PC polymer and effective field intensity theory. The measured dielectric constants of PZT/PC are in good agreement with the calculated values for the composite with a very small PZT volume fraction, based on the Onsager effective-field theory. The poling condition under an external electric field was optimized by effective field intensity theory. It was found that the optimized poling temperature is near 170 ◦C, but not near Tg [85].

For films prepared by sol-gel processing, it is shown that the switchable polarization is decreased at the grain boundaries with respect to the grain volumes. The coercive field is clearly increased at the grain boundaries [86].

From past investigations using short cracks, which were produced with Vickers or Knoop indentations, it is well known that electrically poled piezoelectric ceramics exhibit strongly anisotropic fracture toughness. This is mainly attributed to the different switching ability of domains lying in the crack tip stress field. Both poling direction as well as degree of polarization has to be considered. While most investigations focused on indentation techniques, only very few publications on R-curve behaviour in ferroelectric materials are known. The question of the full influence of poling, however, has not been addressed yet. Previous MTech. Nanoscience and Tech.

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researchers agreed that toughening is attributed to a process zone mechanism similar to transformation toughening, with domain orientation being an additional complicating feature in ferroelastic switching. A systematic analysis for long cracks was possible using compact tension specimens that were poled along the respective edges and compared to the unpoled material. Poling in the thickness direction yielded the material with the highest fracture toughness while the direction parallel to the loading direction led to the lowest fracture toughness [87].

A ceramic–ceramic actuator composed of two piezoelectric ceramic layers with opposite poling directions was developed by Chang-Bun Yoon et al. One layer of the actuator had a high coercive electric field while the other had a relatively low coercive electric field. The actuator was fabricated by cofiring a green compact composed of the PZT-I powder on top of the PZT-II powder. When an electric field 41.1 kV/mm was applied to the sintered body, the whole specimen was poled in one direction. Subsequently, by applying a field between 0.6 and 1.1 kV/mm, only the PZT-II layer was switched to the other direction. When an electric field was applied to this oppositely poled two-layer specimen, one layer of the specimen expanded while the other layer shrank. As a result of these reverse dilations, the actuator was bent into a dome shape, yielding a large axial displacement at the center [88].

Shunji Watanabe et al. found that poling the PZT film formed by sputtering and then annealed at 650 °C in air was as effective as poling bulk PZT ceramics [89].

Piezoelectric 3–3 composites are often prepared from unpoled PZT ceramics and polymer matrices. During the poling process the PZT cannot deform freely due to the clamping by the surrounding polymer, which after poling results in the occurrence of residual mechanical stress in the composite. Based on the multi-linear constitutive model of ferroelectric and ferroelastic piezoceramics, a nonlinear finite element analysis was performed within the representative volume element to model the poling behaviour of this kind of composites, in which appropriate periodic boundary conditions were prescribed for the displacements and the electric field of the composites. The results show that if volume fraction is less than 18% a portion of the compressive mechanical stress in the poling direction on the PZT ceramic may cause a mechanical depolarization of the PZT ceramic [90].

The Young’s modulus (Y11) of the PZT film was 80 GPa. Poling at 40 kV/cm, 250 °C for 20 min increased the properties by a factor of 4.0–5.5, resulting in the piezoelectric coefficient (d31) varying from 80 to 180 pm/V. The deposition rate of 20 mm/min was extremely high as MTech. Nanoscience and Tech.

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compared with conventional thin-film technologies. A poling procedure with heating is very effective to improve the piezoelectric strain. The hysteresis of an unpoled sample with frequency driving is almost close to zero. Mechanical and piezoelectric properties are comparable with conventional thin-film technologies [91].

The poling process is investigated theoretically by a nonlinear finite element method modelling, which takes into account the ferroelectric and ferroelastic properties of PZT ceramics. Furthermore, an analytical model is developed, which predicts the remnant strain of the composite and the residual mechanical stress. The compressive residual mechanical stress acting on the PZT in the poling direction increases continuously with decreasing volume content Va of the PZT ceramic. For values of V a higher than about 20%, it is lower than half of the coercive stress necessary to cause a mechanical depolarization. For V a lower than 20% the residual stress rises rapidly. It may cause a mechanical depolarization of the PZT ceramic for Va <11%. With increasing volume content, the longitudinal and the transversal components of the remnant strain increase monotonously in similar way like the corresponding linear effective piezoelectric coefficients [92].

The morphotropic phase boundary in ferroelectric materials, along with the associated strong piezoelectricity, can be created, destroyed, or even replaced by another morphotropic phase boundary through phase transitions during electrical poling. In-situ TEM experiments, supported by piezoelectric property measurements from bulk samples, have unambiguously demonstrated that poling fields may irreversibly destroy or create MPBs and the associated piezoelectricity enhancement. The results point out that, in addition to the virgin-state phase structure, the ferroelectric-to-ferroelectric phase transitions during poling must also be comprehensively studied to fully understand the microstructural mechanism of the macroscopic piezoelectric behaviours [93].

Pulsed DC sputtered and RF sputtered PZT films were deposited on platinized silicon substrates. The dominant crystalline orientation peaks of both the films were analyzed. The fracture surface morphology of pulsed DC sputtered film exhibited porous grains, compared to dense layers in RF sputtered film. The ξ r values were close to 1000 in both the films. After poling, there was a shift in C-V and P-E curves due to asymmetric distribution of oxygen vacancies at platinum electrode and PZT film interface. Poled films had significant increase in e31 values. But the values were still low due to the fact that non 180° domain wall pinning is still higher due to oxygen vacancies at the interface [94].

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Composites of lead zirconate titanate ceramic particles dispersed in non-ferroelectric polymers of different electrical conductivities (polyurethane and polyethylene) have been prepared and poled under ac fields of different amplitudes Ea and frequencies f. The poling efficiency of the composites (as indicated by the observed remnant polarization PCR) is strongly dependent on the frequency of the poling field and the electrical conductivity of the polymer matrix. A lowfrequency ac field and a high-conductivity polymer matrix would make the poling become more effective. The phenomena can be understood by the simple theoretical model, in which space charges are allowed to accumulate at the particle–matrix interfaces. The increasing trend of PCR with decreasing f predicted by the model agrees well with the experimental results. It is suggested that the poling process is mainly governed by a crucial parameter ‘relaxation time’ τ of the interfacial charge. If the poling time is longer than τ, the interfacial charge can accumulate at the interfaces to stabilize the aligned dipoles in the ceramic phase, and hence the composite becomes poled. Otherwise, the composite cannot be effectively poled even under a high electric field [95].

The poling behaviour of a lead-zirconate-titanate piezoelectric ceramic is investigated by measurements of the ferroelectric hysteresis, the longitudinal piezoelectric coefficient, and field-cooling poling experiments. At high temperatures, the decrease in the coercive field facilitates poling at lower electric fields, resulting in higher values of the longitudinal piezoelectric coefficient. However, there exists a threshold field of about 150 V/mm, below which fully poled samples cannot be obtained even when field cooling from temperatures above the transition. Further, a temperature regime below the Curie temperature is observed, where a polarization under field can be measured, but a remnant polarization is not stable [96].

Size Effects.

The processing, electromechanical properties, and microstructure of lead zirconate titanate (PZT) ceramics over the grain-size range of 0.1–10 µm were studied by Clave A at al. Using measurements over a large temperature range (15–600 K), the relative role of extrinsic contribution (i.e., domain-wall motion) was deduced to be influenced strongly by the grain size, particularly for donor-doped PZT. The MPB is an almost-temperature-independent phase boundary that separates two ferroelectric phases, the tetragonal and the rhombohedral. .

Compositions near the MPB may have both of these phases coexisting to give a total of fourteen possible polarization directions (six tetragonal 〈001〉 and eight rhombohedral 〈111〉— in reference to the cubic prototype cell axes). The large number of polarization directions MTech. Nanoscience and Tech.

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enables optimized crystallographic orientations to be established from grain to grain in the poling process and, in turn, results in anomalously high piezoelectric properties. Further improvements are made to the electromechanical properties through compositional modifications. Donor and acceptor doping are used to obtain so-called ‘‘soft’’ and ‘‘hard’’ PZT materials, respectively [97].

Figure : Dielectric and piezoelectric properties of undoped and commercial PZT composites [97].

Using carefully processed ceramic samples that are free of space-charge contributions, as indicated by the adherence to the Curie–Weiss relation, the grain-size variation in the range of 0.1–10 mm is shown to be sensitive to domain structural changes, which, in turn, limits the elasto-dielectric properties through the extrinsic contributions. The domain variants are limited in the ultrafine grain material; however, the relative domain density is increased, as indicated from the departure from the parabolic scaling of the mode of the domain size distribution and the mean of the grain size. The reduction in the variants lowers the saturation polarization, the piezoelectric coefficients and electromechanical coupling coefficient. The relative increase in dielectric loss with decreasing grain size could be explained only by the relative increase in domain density, as indicated by the smaller domain sizes.

Figure :Elasto-dielectric trends for PZT ceramics [97].

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P. I. Bykov et al. have performed for the first time a calculation of the ferroelectric size effect of cone-shaped nanoparticles (nanocones). To solve the appropriate Euler-Lagrange equations, a direct variational method was used. An approximate analytical expression for the phase transition temperature dependence on nanocone height and half-angle was derived. P. I. Bykov et al. have shown that the transition temperature may be higher by a factor of up to 2.5 compared to bulk materials. Similar to nanowires, the transition temperature T cl to the nonpolar state is enhanced for negative electrostriction coefficients Q12. However, in nanocones this enhancement exceeds that one of nanowires (Tcl/TC increases up to 2.5 times compared to 1.5 times in an optimized nanowire). As a consequence, P. I. Bykov et al. obtained an also higher spontaneous polarization [98].

Hard (Mn-doped) PZT ceramics having grain sizes in the range 4 to 9 μm were subjected to an AC electric field with an amplitude E 0 of 0.1 to 3.5 kV mm-1. The dielectric characteristics were determined by analysis of the measured P-E (polarization-electric field) hysteresis data. It was found that the saturation polarisation Ps, measured at field amplitude of 3.5 kV mm -1, reduced from 29 to 21 pC cm -2 as the grain size reduced from 7.1 to 4.1 μm, indicating an increased resistance to ferroelectric domain switching in the fine-grained material. In contrast, the dielectric permittivity and loss (εr/,εr//), measured in the field range below the coercive field Ec, both increased with a reduction in grain size; this was attributed to an increase in the domain wall density in fine-grained ceramics. Near-linear εr/-E0 plots were obtained for 0.3 kV mm-1-<Eo<l.7 kV mm-1, giving a good fit to the Rayleigh Law. Rayleigh coefficients of 0.81 x l0-3, 0.64 x l0-3 and 0.53 x 10-3 m V-1 were obtained for hard PZT ceramics having grain sizes of 4. I, 7.1 and 8.9 μm respectively [99]

Characterization Porous lead zirconate titanate (PZT) ceramics are widely used because of their low acoustic impedance, high figure of merit and high hydrostatic sensitivity. Porous PZT ceramics were fabricated by incorporating polyethylene oxide (PEO) as pore-forming agent. Both PZT powder and PEO were mixed with a binder at different ratios and compaction was carried out.

The samples were slowly heated to remove the pore-forming agent and binder without cracks, followed by controlled sintering and electrode-forming. Samples were poled using corona poling technique. The density of the specimen decreases with increase in the amount of PEO, which subsequently decreases the acoustic impedance of material to be matched with water.

Consequently as the density of the material decreases its porosity increases followed by MTech. Nanoscience and Tech.

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subsequent increase in the hydrostatic coefficients. It is observed that hydrostatic charge coefficient (dh) increases with increase in the amount of PEO. The peak value of d h was observed at (50/50) PZT/PEO. The improved dh with this composition of porous PZT ceramics is due to the effective anisotropy in the microstructure which also decreases the dielectric constant of the specimens. Similarly hydrostatic voltage coefficient (gh) also increases with increase in the amount of PEO. The gh increases in porous PZT ceramics because of its higher dh values. This is because, air replaces high value dielectric PZT phase at low permittivity, and increases the gh value. In reality, continuously increasing the gh without decreasing ceramic volume is not practically possible as permittivity decreases, the capacitance declines to a level where its use as an active element for a hydrophone becomes unacceptable. Figure of merit (FoM) increases with an increase in the amount of PEO. Because d h and gh values increase with increase in the amount of porosity which subsequently increases the FoM values since it is a product of dh and gh. The d33 values of porous PZT ceramics are considerably lower than that of the conventional PZT ceramics, and also it decreases with increase in the amount of PEO. The d33 value of porous PZT ceramics is lower than that of conventional PZT ceramics because of the existence of the non-piezoelectric air phase. Scanning electron micrographs shows that, when amount of PEO increases the porosity also increases; this subsequently increases the interconnectivities between the pores and pore sizes. Irregular distribution of pores (mixture of 3–3 and 0–3 connectivity) is seen in the low porosity microstructure whereas uniform distribution of pores (3–3 connectivity) is seen in high porosity microstructures. It also shows wide range of pore distribution varying from small micro pores to few macro pores. This change in microstructure is due to the amount of pore forming agent used during the processing of porous PZT ceramics [100].

Mechanical Properties In the study of crack growth into ferroelectrics domain structure, it has been shown, that in the case of the ferrosoft ceramic there are mechanisms that causes the prevalent toughening to compare with micro cracking near crack, branching and bridging of the crack. There are three mechanisms of the crack dragging at 900 domain boundaries, namely (i) by crack plane orientation change, (ii) by crack interaction with non-coherent boundary,

and (iii)

by

boundary with absorbed impurity. The simulated results confirm the known trend of the fracture toughness rise with grain size in the limits of this region. The qualitative trends of the FC toughness and strength vs. crack length in the conditions of the crack bridging are found.

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These parameters have not simple dependencies on the grain size thanks to the effects of micro cracks at the grain boundaries. By the definite selection of the characteristic bridge spacing, d, it is possible that the micro cracking will find ceramic strength covering the effects of the crack bridging [101].

Table : Computer simulation results for PZT press-powder sizes [101]

The PZT films, with a composition near the morphotropic phase boundary (MPB), were epitaxially grown on (001) MgO substrates and then micro fabricated into a rectangular shape.

Lateral electrodes were deposited on both sides of the PZT films to apply an external electric field perpendicular to the polarization. A sinusoidal input voltage of 100 kHz was applied between the lateral electrodes and in-plane shear vibration was measured by a laser Doppler vibrometer. In-plane displacement due to shear mode piezoelectric mode vibration was clearly observed and increased proportionally with the voltage. Finite element method (FEM) analysis was conducted to determine the horizontal electric field in the PZT film. In-plane vibration was clearly observed, and the displacement increased proportionally with the voltage. Since the PZT was a self-polarized c axis oriented film, the generated strain is caused by the intrinsic shear piezoelectric effect without the other piezoelectric strains [102].

A novel piezoelectric energy harvesting module with controllable strain was designed to allow investigations into the correlations among strain, frequency, and output power. Specifically, although conventional vibration modules allow control over strain only through variation in tip mass, the proposed module allows more accurate strain control through adjustment of the displacement of the free end of the cantilever (5â&#x20AC;&#x201C;45 mm). Experiments showed that both types of modules exhibit an increase in open circuit output voltage with strain, but the piezoelectric material fails at severe strain. In addition, it was confirmed that the proposed module design can keep the output voltage constant by controlling the strain, which allows investigation into the relationship between frequency and output power. Thus, at constant strain, the matching MTech. Nanoscience and Tech.

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impedance was found to be low at high frequency. Therefore, optimum conditions for harvesting maximum power are high frequency and the largest strain that does not damage the piezoelectric material [103].

Structural Health Monitoring (SHM) systems allow for permanent and online characterization of condition and health of structural components. S Gebhardt et al. introduced novel SHM modules fully based on inorganic materials which show distinguished improvements of temperature and chemical stability compared to known piezoceramic-polymer-patches. Using ceramic multilayer technology lead zirconate titanate (PZT) discs are integrated into a package of low temperature cofired ceramic (LTCC) sheets enabling for the production of compact ultrasonic transducers with integrated electronic circuits and signal processing units [104].

Lead zirconate titanate (PZT) ceramics has characteristics of not only piezoelectricity but also flexoelectricity. Piezoelectricity is a phenomenon that electric polarization is induced by strain, and flexoelectricity is the one that the polarization is induced by strain gradient. In this study, flexoelectricity in poled soft PZT ceramics is measured. In order to eliminate influence of piezoelectricity, PZT ceramic thin plates are subjected to pure bending using four-point bending experimental mechanism. Strain gradient along the direction of thickness in the plate is caused by the bending motion. Electric charge between two electrodes which is set on the center of the plate surface is measured under quasi-static sinusoidal load. Even though the polarization for piezoelectric effect is eliminated by the experimental setup, the influence of piezoelectric effect still remains since polarization by piezoelectricity is much larger than the one by flexoelectricity. So the influence of piezoelectricity is eliminated using qualitative difference between piezoelectricity and flexoelectricity for poling direction. Influence of piezoelectric effect is cancelled by pure bending of thin plate specimen and by taking average between the results of different bending direction [105].

Ring-shaped lead zirconate titanate (PZT) piezoelectric vibrators were subjected to nonuniform mechanical stress applied by bolt clamping. The effect of mechanical stress on the effective electromechanical coupling factor (keff) and mechanical quality factor (Q m) of the thickness and wall thickness modes was studied by an equivalent electric circuit analysis. The initiation and propagation of cracks under mechanical stress were also discussed based on the resonance method and the indentation technique. keff for both the thickness and wall thickness modes decreased with increase in mechanical stress due to de-poling of the PZT. Q m of the

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thickness mode dropped sharply with increase in mechanical stress while Q m of the wall thickness mode remained almost unchanged. The following conclusions was drawn: 1. Formation of a micro crack in a PZT ring under a torque can be detected by the occurrence of spurious vibrations at the wall thickness mode in the electrical impedance vs. frequency spectra.

2. Formation of a micro crack can also be detected from the resonance or anti-resonance impedance vs. torque spectra. The resonance impedance changed sharply when a crack had formed in a piezoelectric vibrator.

3. Effective electromechanical coupling factor of the PZT ceramics decreases with increase in torque. The change of mechanical qualify factor for the thickness mode is much faster than that for the wall thickness mode [106].

A.Yu. Belov and W.S. Kreher presented a viscoplastic (rate-dependent) constitutive model describing both hysteretic and sub-coercive behaviour of ferroelectric ceramics. Viscoplastic models employ rate equations for the volume fractions of orientation variants along with a distribution function for grain orientations, providing a statistical macroscopic description for the processes of polarization reversal in polycrystalline ferroelectrics. A viscoplastic constitutive model for ferroelectric ceramics has been presented to include irreversible ferroelectric switching at low and high loading levels. Here attention is focused on two viscoplastic models for perovskite type ferroelectrics undergoing a cubic-to-tetragonal phase transition. Both models incorporate 90◦ and 180◦ domain switching, but differ in a number of representative domain orientations, which is 6 and 42, respectively. Different parameterisations for the models were tested, with a special emphasis on orientation effects in the behaviour of poled ferroelectrics under multi-axial loading as well as on rate effects. Simulation of the polarization rotation in soft PZT ceramics by electric field applied at an angle to the original poling direction show good agreement between the predictions of the viscoplastic model and experimental data [107].

A common design of piezoelectric micro actuators adopts a membrane structure that consists of a base silicon structure, a layer of bottom electrode, a layer of piezoelectric thin film, and a layer of top electrode. In particular, the piezoelectric thin film is often made of lead–zirconate– titanate (PZT) for its high piezoelectric constants. When driven electrically, the PZT thin film extends or contracts flexing the membrane generating an out-of-plane displacement. For PZT MTech. Nanoscience and Tech.

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thin-film micro actuators, residual stresses are unavoidable from fabrication and can significantly reduce the actuation displacement. Cheng-Chun Lee et al. present a fourfold approach to address the issue of residual stresses. First, we demonstrate experimentally that two PZT thin-film actuators may present substantially different displacement and natural frequency even though dimensions of the two actuators are similar. Through a series of finite element analyses, we conclude that only residual stresses can produce such a significant frequency shift reducing the displacement of a PZT thin-film micro actuator. Second, we measure the warping of the PZT thin-film actuator via interferometry to detect residual stresses. A simple calculation using shell theories indicates that the warping only causes a tiny shift in natural frequencies. Therefore, most of the degradation of actuator performance results from the nature that residual stresses are in-plane rather than the warping caused by the residual stresses. Third, Cheng-Chun Lee et al. developed a vibration analysis to determine when residual stresses could significantly reduce actuator displacement [108].

Effects of compressive stress on the dielectric and ferroelectric properties of commercial soft PZT ceramics were investigated. The dielectric and ferroelectric properties were measured under compressive stress applied parallel and perpendicular to an electric field direction. The results showed that the dielectric properties; i.e. the dielectric constant (ε r) and dielectric loss tangent (tanδ), and the ferroelectric characteristics; i.e. the area of ferroelectric hysteresis (P-E) loops, the maximum polarization (Pmax), the coercive field (Ec) and the remnant polarization (Pr), changed significantly with increasing compressive stress. These changes depended greatly on direction of the applied stress. The stress clamping of domain wall, de-ageing and non-180 ◦ ferroelectric domain switching processes are responsible for the changes observed. In addition, a significant decrease in those parameters after a full cycle of stress application has been observed and attributed to the de-poling and stress-induced decrease in switchable part of spontaneous polarization at high stress. In general, with increasing compressive stress the dielectric constant increases, while the dielectric loss tangent decreases when the stress is applied parallel with the electric field direction. Interestingly, the observed changes of the dielectric properties with the perpendicular compressive stress are opposite to those under the parallel stress. The ferroelectric characteristics, i.e. the area of the ferroelectric hysteresis (P-E) loops, the maximum polarization (Pmax), the remnant polarization (Pr) and the coercive field (Ec) decrease with increasing compressive stress in both stress cases. The non-180◦ ferroelectric domain switching, stress clamping of domain wall, de-ageing processes, as well as

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the stress-induced decrease in switchable part of spontaneous polarization and the de-poling mechanism, are responsible for the changes observed [109].

The propagation process and the anisotropy of the indentation cracks of poled PZT-5H ferroelectric ceramics in air and water under sustained load were investigated using Vickers indentation equipment. It is found that the length of the indentation cracks increased with increasing time to keep indentation load in air and water. Thus, sub-critical crack growth or stress corrosion cracking (SCC) under sustained load occurred. For the cracks parallel to the poling direction, the threshold stress intensity factor for cracks arrest, K ISCC, is larger, whereas the crack propagation rate, da/dt, is smaller than those for the cracks perpendicular to the poling direction. The anisotropy of susceptibility to SCC is related to the anisotropy of fracture toughness. The larger the fracture toughness is the more susceptibility to SCC is, that is, the smaller the KISCC is, the larger the da/dt is [110].

The crack propagation behaviour in piezoelectric lead zirconate titanate (PZT) ceramics is studied. The crack propagation in piezoelectric ceramics under pure mechanical loading is considered in which a mode I mechanical loading is applied by means of Vickers indentation.

Anisotropy in crack propagation is characterized by measuring the length of cracks in two mutually orthogonal directions. Residual stresses in the PZT are also characterized by an indentation technique. The results indicate that as-fired and unpoled piezoelectric ceramics are isotropic in properties and under compressive state of residual stress. Poling introduces anisotropy in crack propagation and changes the residual stress state. A compressive state of residual stress in the poling direction and a tensile stress state perpendicular to the poling direction are measured. This change in the residual stress state is related to the 90 0 domain reorientation and associated dimensional change induced by the applied electric fields during poling. In the unpoled PZT ceramics, the crack propagation was isotropic, and there was a compressive residual stress of 25.1 MPa because of volume increase or texture near the surface associated with cubic to tetragonal phase change at the Curie temperature or compositional gradients created during sintering because of the PbO loss or enrichment near the surface.

Crack propagation became anisotropic after poling. Cracks propagated more in the direction perpendicular to the poling direction than in the parallel direction. Residual stress states in the PZT material were also changed by poling. In the direction parallel to poling there was a compressive stress of 16.1 MPa, while a tensile stress of 6.3 MPa normal to the poling direction was found. This change in the residual stress states was believed to be related to the 900 domain reorientation and the corresponding dimensional changes induced by the applied MTech. Nanoscience and Tech.

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electric fields during poling. It was noted that the anisotropy in crack propagation cannot be explained by the residual stresses present in the poled PZT ceramics, but it may be rationalized by the domain switching mechanism [111] The possibility of machining brittle materials using single point diamond turning in a ‘ductile mode’ has been investigated by many researchers in recent years. The ability to machine ferroelectrics in a ductile manner and by so doing reduces sub-surface damage, could eliminate the need for subsequent lapping and polishing and thus reduce production costs. Fracture mechanics techniques were used to investigate the localised elastic/plastic behaviour. PZT ceramics in the poled and unpoled state were single-point diamond-turned under different machining conditions and ductile machining has been achieved. It is suggested that the strain generated by reorientation accounts for brittle damage [112] Compact tension tests and indentation-fracture tests have been conducted to study the effects of an applied electric field on the fracture toughness (K IC) of poled commercial lead zirconate titanate (PZT) ceramics. The experimental results show that an applied electric field, either parallel or antiparallel to the poling direction, considerably reduces the K IC value of the PZT ceramics. The reduction in KIC for a negative field is larger than that for a positive field of the same strength. The failure mode in the PZT ceramics is basically trans granular, insensitive to the applied electric field [113].

Tensile tests were carried out on unpoled and poled soft lead zirconate titanate (PZT) ceramic materials: APC #855 (APC International) and PZT-5H (Morgan Electro Ceramics). The tests were performed on a dog-bone specimen with holes at its edges. A methodology is presented for carrying out these tests. A tensile stress was applied by means of Kevlar strings through the specimen holes. The poling direction was perpendicular to the longitudinal specimen axis. For the poled specimens, two electrical boundary conditions were applied, namely, E= 0 and D= 0.

Strains were measured at four points on the sample. For each specimen, the bending percentage was calculated. For all specimens, stress–strain curves were found to be initially linear; at a strain of approximately 0.0001, the curves became nonlinear. Young’s modulus was measured in the linear region of the stress–strain curve. Young’s modulus values were highest for the poled material with an open circuit boundary condition (D= 0) and lowest for the unpoled material [114].

Influence of uniaxial pressure 0–1000 bars applied parallel to or perpendicularly to the ac or dc electric field in one-dimensional or two-dimensional manner on dielectric and ferroelectric MTech. Nanoscience and Tech.

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properties of hard lead zirconate titanate PZT ceramics were investigated. The experimental results revealed that applying uniaxial pressure leads to a reduction in the peak intensity of the electric permittivity ε, of the frequency dispersion as well as of the dielectric hysteresis.

Moreover, with increasing pressure the peak intensity of ε becomes diffused and shifts to a higher temperature. It was also found that simultaneous application of uniaxial pressure and electric field perpendicular to each other in the poling process improves the ferroelectric properties. This indeed indicates new possibility for poling materials with a high coercive field and/or high electric conductivity. The effects of uniaxial load are weaker than that obtained for soft PZT ceramics [115] The effects of applied dc electric fields of ±10 kV/cm on the modulus of rupture of poled PZT841 ceramics were studied using three-point bending tests. At each level of the applied electric field, 54 or 55 samples were tested and the data were statistically analyzed. The results showed that the measured moduli of rupture followed a Weibull distribution with a Weibull modulus of 10.6 when no electric field was applied. When the applied electric field was either parallel or antiparallel to the poling direction, the distribution of the modulus of rupture revealed two peaks and was fitted by a two-peak Weibull distribution. One peak occurred at about 95 MPa, approximately the same as that without the presence of the applied electric field, while the other peak occurred at around 50 MPa under either a positive or a negative electric field.

Obviously, either a positive or a negative electric field assisted the applied mechanical loading to fracture the samples [116] Tests were carried out on the behaviour of a crack in piezoelectric material in which the crack is parallel to the poling direction where four-point bend specimens made of PZT-5H (Morgan Electro Ceramics, Wrexham, UK). Cracks were introduced parallel to the poling direction.

With an electric field induced perpendicular to the cracks, the load was increased until failure occurred. Using the load at fracture, the level of the electric field and the critical crack length as well as finite element analyses were carried out to determine the intensity factors [117] The major problem in the production process of efficient ultrasonic transducer is the preparation of defect-free PZT fibres. A considerable amount of empirical work is presently in progress to achieve this goal of special importance for high sensitive transducers. However, there is a lack of basic research on the detection of residual stress and defects areas in these fibres due to difficulties in mechanical examination of such flexible elements. With the use of the nanoindenter for material characterisation of PZT fibres obtained by extrusion method, L. MTech. Nanoscience and Tech.

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Kozielskiet al. clarified phenomena of sudden depth-excursions during indentation on the edge of fibres [118].

Hong et al. investigated the effects of strain and crack formation on the performance of piezoelectric materials as well as methods to repair damaged electrodes and reinforce the piezoelectric material. Specifically, this study investigated whether Ag paste (thickness: 0.1 mm) could restore electrical contact in damaged electrodes, and whether a coating of UVcurable resin could provide reinforcement against crack formation. Experiments were conducted with a piezoelectric material on a steel cantilever substrate. The substrate was subjected to impact at various distances from the free end of the piezoelectric material to vary the applied strain. It was found that the output voltage increased with the strain (distance of impact from free end) until crack formation, which led to a large decrease in output. However, Ag paste could successfully restore electrical contact. Furthermore, before crack formation, coating with UV curable resin increased the maximum strain, and therefore, maximum electrical output, as well as cycle life [119] The topic of multifunctional material systems using active or smart materials has recently gained attention in the research community. Multifunctional piezoelectric systems present the ability to combine multiple functions into a single active piezoelectric element, namely, combining sensing, actuation, or energy conversion ability with load-bearing capacity.

Quantification of the bending strength of various piezoelectric materials is, therefore, critical in the development of load-bearing piezoelectric systems. Three-point bend tests are carried out on a variety of piezoelectric ceramics including soft monolithic piezoceramics (PZT-5A and PZT-5H), hard monolithic ceramics (PZT-4 and PZT-8), single-crystal piezoelectrics (PMN-PT and PMN-PZT), and commercially packaged composite devices (which contain active PZT-5A layers). A common 3-point bend test procedure is used throughout the experimental tests. The bending strengths of these materials are found using Euler-Bernoulli beam theory to be 44.9 MPa for PMN-PZT, 60.6 MPa for PMN-PT, 114.8 MPa for PZT-5H, 123.2 MPa for PZT-4, 127.5 MPa for PZT-8, 140.4 MPa for PZT-5A, and 186.6 MPa for the commercial composite.

The high strength of the commercial configuration is a result of the composite structure that allows for shear stresses on the surfaces of the piezoelectric layers, whereas the low strength of the single-crystal materials is due to their unique crystal structure, which allows for rapid propagation of cracks initiating at flaw sites. The experimental bending strength results reported, which are linear estimates without nonlinear ferroelastic considerations, are intended for use in the design of multifunctional piezoelectric systems in which the active device is MTech. Nanoscience and Tech.

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subjected to bending loads. The bending strength values of the qP10n composite samples exhibited a considerable amount of variation and are much greater (186.6 MPa) than those of the monolithic materials, which is attributed to the high-shear-strength epoxy used to bond the PZT-5a and Kapton layers [120] The PZT particles distribution in the polymer matrix, polyvinylidene fluoride (PVdF) obtained from Sigma Aldrich, was analyzed using SEM studies by T Greeshma et al. The amount of crystallinity was found to decrease with decrease in particle size, which in turn decreases the piezoelectric coefficient. The investigation reveals that the dispersed reinforcement influences the crystallization kinetics of PVdF polymer chain, thereby promoting localized amorphous regions, which decreases the piezoelectric coefficient [121] A thermodynamic analysis was carried out to investigate the role of dislocations in ferroelectric materials by S. P. Alpay et al. Due to the coupling of the stress field of the dislocation and the polarization; there is a drastic variation in the polarization near the dislocation. These polarization gradients result in strong depolarizing fields that suppress the polarization in a region that extends over several nanometres. In epitaxial ferroelectric films, these polarization gradients should result in the formation of dead layers that severely degrade ferroelectric properties. The detrimental effect of such regions will be enhanced in ultrathin ferroelectric thin films, and hence play a critical extrinsic role in size effect studies of ferroelectrics [122] A soft PZT is tested in compression; the influence of stress rate seems to be negligible and the material accommodates to cyclic mechanical loadings. These responses are simulated by means of a phenomenological model taking into account the coupling between remnant strain and polarization thanks to a mechanically induced depolarization function. The experimental results are simulated qualitatively and almost quantitatively by the model and parameters identified for one type of soft PZT. On the other hand, bi-dimensional tests on convenient structures should permit to propose and validate a multidirectional formalism of the model among the possible formulation. Nevertheless in the present model the internal variables are found to be coupled. The remnant polarization does not keep track of the microstructural state of the material directly because different configurations of the volume fraction of ferroelectric domains may lead to the same polarization state (remember for example the case of a totally depolarized ceramic under stress and an unpoled ceramic, which respond differently under the same mechanical loading). The approach based on phenomenological theory is however well adapted for loadings close to uniaxial including cyclic ones [123] MTech. Nanoscience and Tech.

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The effect of uniaxial pressure 0–1000 bars applied parallel or perpendicular to the ac electric field on electric properties of soft PZT ceramics has been investigated. It was found that uniaxial pressure significantly influences these properties. With increasing pressure the peak intensity in the ε(T) curve decreases, becomes diffuse and shifts to a higher temperature, dielectric hysteresis is reduced, and dielectric dispersion decreases. It was shown that the application of pressure perpendicular to the electric poling direction improves the ferroelectric properties [124].

A study of specific heat and thermal expansion of PLZT-9/65/35 ceramics in the 150–800 K range of temperatures is reported by S. N. Kallaev et al. Specific diffused features in behaviour of heat capacity and thermal expansion are revealed in the 250–650 K and 330–550 K range of temperature, respectively, and shown to be the result of the growth and changes of a system of ordering nano-size polarised regions. The features of heat capacity in the 250–650 K range of temperature are found to be related to two-level states (the Schottky anomaly). S. N. Kallaev et al. suggest the following.

1. Specific behaviour of heat capacity in the 250–650 K range and of thermal expansion in the 330–560 K range is due to the growth, changes and interactions in the system of reorienting nano-size polar regions.

2. The nature of thermal behaviour of heat capacity and surplus value in the PLZT 9/65/35 ferroelectric relaxor confirms the absence of a macroscopic thermodynamic phase transition in the region of the maximum of dielectric permittivity.

3. At decreasing the temperature of PLZT 9/65/35 ceramics locally polarised randomly distributed nano-regions emerge within the non-polar cubic phase around the Burns temperature Td ≈650 K while the macroscopic polarisation does not appear as far down as the room temperature. A noticeable rhombohedric distortion of the lattice affecting the thermal expansion occurs at T =560 K providing additional contribution to α (T).

Three characteristic temperatures are known in ferroelectric relaxors: T c– the temperature of transition from relaxor to normal ferroelectric state (corresponds to the temperature of depolarisation at heating of a polarised sample), Tm– the temperature of the maximum of dielectric permittivity, and Td – the temperature of emerging nano-scale polar regions (the Burns temperature) [125].

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Energy Harvesting Hiroshi Maiwa et al. performed Thermal and Vibrational Energy Harvesting Using PZT- and BT-based Ceramics [126]. Hongping Hu et al. did work on a piezoelectric springâ&#x20AC;&#x201C;mass system as a low-frequency energy harvester [127].

Chih-Ta Chen et al. developed an extremely cost-effective mechanism for converting wind energy into electric energy using piezoelectric bimorph actuators at small scale [128]. A piezoelectric energy harvester consists of a spiral-shaped piezoelectric bimorph to transfer mechanical energy into electric energy, an electrochemical battery to store the scavenged electric energy, and a rectifier together with a step-down dc-dc converter to connect the two components as an integrated system [129].

Using linear and nonlinear energy harvesters, M. Amin Karami and Daniel J. Inman powered pacemakers from heartbeat vibrations [130]. Using PZT nanofibers, Xi Chen et al. developed a 1.6 V nanogenerator [131].

A piezoelectric transducer for harvesting energy from ambient mechanical vibrations/strains under pressure condition was developed by Xiaotian Li et al. [132]. Kiyotaka Wasa et al. found out that ferroelectric PZT thin films will be suitable for a fabrication of the piezoelectric energy harvesting (EH) MEMS due to their extremely high piezoelectric coefficients [133].

Ideal thermodynamic cycles are presented for an electro-mechanical energy conversion process

by Wen D. Dong et al. [134]. Shashank Priya discusses the various criteria for material selection in design of bulk piezoelectric energy harvesters [135]. Daniel Guyomar et al. discussed energy harvesting based on FE-FE transition [136]. Single crystals and nonlinear process were adapted by Adrien Badel et al. and obtained outstanding vibration-powered electrical generators [137]. As sensors for a wide array of applications continue to shrink and become integrated, increasing attention has been focused on creating autonomous devices with long-lasting power supplies. To achieve this, energy will have to be harvested from the sensorsâ&#x20AC;&#x2122; environment was the idea of Nicholas S.Hudak and Glenn G.Amatucci [138].

Multimodal Energy Harvesting Skin was conceptualized by Soobum Lee and Byeng D. Youn [139]. The mechanism suggested by R. Ambrosio et al. is interesting. Harvesting energy from ambient vibrations to convert it into electrical energy is possible using piezoelectric elements; the energy can be stored and used to bias low power electronic devices [140]. R. Shukla et al.

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discuss about a single crystal power generator [141]. Hong Chen et al., discuss their idea of embedding power harvesters in orthopaedic implants [142] **********

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EXPERIMENTAL Our research basically caters to the need of energy conservation. The main reason why we have focused on the concepts of hard piezoceramics of PZT is that not only are we avoiding the use of physical vapour deposition and chemical vapour deposition tools and that we are also promoting the possibility of large scale production techniques feasible to bring down the cost whenever it becomes part of a manufacturing inception. Speaking in terms of a purely chemistry perspective, intrinsic double ionized lead vacancies and oxygen vacancies simultaneously exist within PZT compositions and create a defect dipole. The acceptor dopants with a valence of +3 induce extrinsic single ionized oxygen vacancies whereas donor dopants with a valence of +5 induce extrinsic single ionized lead vacancies. An electron exchange can exist between single and double ionized vacancies that it was facilitated in the case of single ionized lead vacancies. As a consequence, such a transfer occurred mainly for soft PZT and almost never for hard PZT [143].

Chemical Synthesis We carried out hydrothermal method of synthesis with the use of our Muffle furnace manufactured by Navyug Pvt LTD. The basis for performing synthesis on the lines of hydrothermal method was that the persons among the pioneers of the hydrothermal method some were acquainted with the affiliates of our university. Fundamentally, we wanted to work with energy generators from piezo as the news of energy harvesters for street humps and lighting of street lights from the storage mechanisms [144] and embedding piezoceramics in concrete were known from the Chinese literatures. The concrete experimental results show that some equivalent parameters perform nonMTech. Nanoscience and Tech.

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monotonicity or hysteresis in the loading cycle. While such hysteresis in some other parameters is so slight that the loading curves and the unloading curves of these parameters match well. In other words, these parameters perform a better monotonicity with the loadings [145].

We were sceptical with the thin film synthesis of piezoelectric materials, for the method of thin films involves the use of physical vapour deposition (PVD) or chemical vapour deposition (CVD), both of which are not mass producible to enable the general public to avail economically. Also, the energy factor played a major role in the choice of materials.

The choices of lead-free materials were ruled out as it were in a nascent stage for procuring the initial materials for a completely unknown application for any of us. we didnâ&#x20AC;&#x2122;t want to rely on the inventors of the hydrothermal methods for the choice of materials as this trial and error were believed to constitute a simplified and a new roadmap for further development of research product during which the replacement for the piezo materials could take place for ensuring environmental factors are taken into considerations.

Also, we sought for a branded maker of steel bomb like the one shown below in the left.

But due to cost factors we landed with the one to the right in the figure.

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Figure : Autoclaves, one with pressure and temperature valves and other without The basic hydrothermal procedure used in this work was first proposed by Deng et al.

[146] for the synthesis of PZT. It is a relatively simple one-step technique that utilises the following precursors in powdered form: ▪Lead nitrate—Pb(NO3)2 ▪Zirconyl oxychloride—ZrOCl2·8H2O ▪Titanium dioxide —TiO2 Experiment was carried out by adding stoichiometric quantities of the precursors to a home-built autoclave with 60 ml capacity. Then water is added up to 3/4 th of its volume.

Finally potassium hydroxide flakes were added slowly, with 1 hour of continuous stirring, to give an initial mineralizer concentration of 5 mol/L. After the hydrothermal treatment the powders were filtered and washed with distilled water and ethanol and then dried in an oven at 60 °C for 8-10 hours. These procedures were replicated exactly during this project. Table 4 shows the adjusted precursor masses for 52:48 PZT and several other stoichiometries, across the solid solution range, which was attempted in this project. The MTech. Nanoscience and Tech.

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precursors were mixed with 25 ml deionised water and 7.013 g KOH to reproduce the 5 M initial mineraliser concentration used by Deng et al. [146]. A standard Buchner vacuum filtration system was used in conjunction with Whatman filter paper, to isolate the product. This trapped the majority of the particles since they had agglomerated after processing. The powders were rinsed using deionised water.

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Filterate Temperature

Date

Sample Code

Pb(NO3)2

ZrOCl 2.8H2O

TiO2

KOH

Start Time

Stop Time

Temperature

Stirr(minutes)

01-02-2012 02-02-2012 03-02-2012

H1 H3 H4

3.312 3.312 3.312

1.675 1.675 1.675

0.383 0.383 0.383

7.67 10.77 10.77

13:40:00 12:00:00 14:00:00

15:07:00 16:00:00

165 164 165

60 30 60

06-02-2012

H51

3.312

1.675

0.383

10.77

10:30:00

12:45:00

165

H52

3.312

1.675

0.383

10.77

14:00:00

17:00:00

08-02-2012

H6

3.312

1.675

0.383

10.77

10:42:00

14:42:00

30

Incomplete Reaction [ small amount of water present]

09-02-2012

H7

3.312

1.675

0.383

10.77

11:05:00

16:05:00

60

Incomplete reaction [small amount of water present].

10-02-2012

H8

3.312

1.675

0.383

10.77

10:32:00

12:32:00

180

60

Little amount of water present

11-02-2012

H9

3.312

1.675

0.383

10.77

11:51:00

14:51:00

180

60

Little amount of water present

17-02-2012

H10

3.312

1.675

0.383

10.77

10:43:00

14:43:00

180

30

22-02-2012

H11

3.312

1.675

0.383

10.77

11:52:00

16:52:00

180

60

21-02-2012 27-02-2012 28-02-2012 29-02-2012 03-03-2012 05-03-2012 06-03-2012 07-03-2012 09-03-2012

H12 H13 H14 H15 H17 H16 EDTA H18 EDTA H19 EDTA H21 H17 H16 H23 H24

3.312 3.312 3.312 3.312

1.675 1.675 1.675 1.675

0.383 0.383 0.383 0.383

15:15:00 13:48:00 14:45:00

60

3.312 3.312 3.312

1.675 1.675 1.675

0.383 0.383 0.383

1.675 0.644 1.933

0.383 0.6391 0.319

7.012 7.012 7.012 7.012

15:52:00 16:42:00 16:30:00 17:32:00 16:20:00 17:15:00

160 160 160 160 125

3.312 3.312 3.312

13:15:00 11:48:00 11:45:00 11:32:00 11:43 AM 13:52:00 12:42:00 12:30:00 13:32:00 12:20:00 12:15:00 12:22:00 10:56:00

190

7.012 7.012 7.012 7.012 7.012 7.012 7.012

H25

3.312

2.25

0.239

7.012

12:54:00

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EDTA

Observations

needle-like structures are formed.

50 50

Needle-like structures was observed Needle-like structures present

0

3.72 3.7224 7.44 3.722 2.521 3.72

of 0.4M of EDTA 0.4M of EDTA of 0.8M EDTA of 0.4 M EDTA of 0.8M EDTA of 0.4M EDTA Zr/Ti =(20:80) (60:40) (70 : 30)0.70 x 322.25 + 0.30 x 79.88

60

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Mechanism Development In the entire scheme of things that nanoscience and technology brings out to the academia, there exists four steps for the completion of the roadmap to realize a nanosystem that is completely autonomous and functional in a distinct arena of activity.We have come to recognize that there is an intermediate phase of instrumentation evolution into a device which was missing in the roadmap, obstructing a complete nanomaterial existence with ubiquous organizational behaviour.

Figure : Structural flow of realization of nanotechnology It is imperative for a researcher to migrate into an arena of technical standards in a short span with a gamut of expensive measurement tools under his sway. However, it is unlikely to find the right equipment among the inventories specific to the affiliated university or institute. Many specialized labs in advanced countries hence do their customization of available instruments under university funding. We have referred to some notable works wherever need be in this work.We infered notable works cited below before undertaking any iterative part of their work.

An apparatus to precisely measure ultrasonic wave velocities in piezoelectric single crystals under varying uniaxial load has been designed and built by some scientists. The apparatus includes two key improvements in the scientific instrumentation: (1) improved alignment of the applied uniaxial bias and (2) the use of the cross-correlation method in analyzing the data in order to more precisely determine the time of flight and corresponding ultrasound wave speed. The apparatus has been used successfully to measure the linear wave velocity versus stress relation such as to enable the accurate extraction of the third-order elastic constants of the single crystals langasite and langatate. The typical measurement results discussed elsewhere by Haifeng Zhang et al.

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illustrate the improved precision in determining the co-efficients controlling the bulk acoustic wave velocities, consistent with an uncertainty analysis based on York’s linear regression method. There, the apparatus can be used to measure the third-order elastic constants of other materials as well [147].

A miniaturized device that integrates tensile and fatigue actuators with dimensions of 196 mm×135 mm×45 mm is developed based on modular idea by Zhichao Ma et al.. The device can be used to investigate the static tensile and dynamic fatigue behaviours of bulk materials. For the tensile actuator, a displacement cor-rection method based on the load sensor compliance is given, the feasibility of the method is carried out on A570 Gr. 33 steel and is verified to present an improvement of calculated elastic modulus and a decrease of calculated elongation, the correction parameters are also compared with the parame-ters obtained by commercial tensile instrument (Instron 3345 model). The fatigue actuator is consisted of a special flexure hinge and piezoelectric stack, combined with the tensile actuator, the device could carry out the in-situ fatigue tests under SEM or metallographic microscope due to the miniaturized dimensions. Principles of the fatigue test are introduced, and the application of testing the storage and loss modulus as a function of frequency is also explained, as the device could real-timely record the specimen’s load and displacement as a function of time [148].

Thus after a study on the above author’s works we tooks some text lessons on where all things come about from a standpoint of our efforts [148a]. We used a stepper motor of Minebea Co, Japan as shown in the data sheets in the table. It has a gear head. Matching gears available in market are made of plastic. We desire to use it to drag a wire rope of steel. This prompted us to obtain customized metal gears. We were vexed with finding 100% ordered gears and its expense and cheap gears with semi-mating nature standard metal gears proved to be a better option. The reason we went for the standard gears is that we were just experimenting with the prototype. We used a transformer with 3A and 12 V step-down capability. We took this decision as we already had a large number of circuits MTech. Nanoscience and Tech.

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with distributed current requirements. We mated the gears with a clamp and attached a heavy gear with standard teeth sizes using some mild steel and bearings of 3mm inner radius. Power transmission losses were not our primary cause of concern. For smaller sizes, the instrument needs to be modified by using a more powerful power supply, actuator with extended frequency and amplitude ranges, cooling of the actuator and the power supply, and the related mechanical modifications of the sample holder[149] Table : Stepper Motor specification

A rod was tapered on the lathe and fitted with bearings and welded. We made wood as the choice for the base because wood can be afforded within reasonable expenses as well as a variety of thicknesses provides a varying degree of rigidity. We understood that an L clamp could connect various orientations of woods. Beware that the metal base for the transformer can actually pass some of the leakage currents and to avoid it, a wire has to be connected to the metal base and put inside a sleave along with the pair of wires of the transformer and connect it with a three pin 3A power plug. Our base is limited to the rare end of the machine. However, it is necessary to protrude the base to a greater length at the front end in order to fix the rectangular gear box and mate it with the heavy free gear that is connected to the stepper motor gear by the gear mating with another smaller gear. The MTech. Nanoscience and Tech.

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dynamics of rotations is a study of a separate subject called control systems in electrical engineering. This study reveals the stability of the electrical system and further, the dynamics of gears and pulleys outside the fixtures and in the rectangular gear box incolves lot of principles of mechanical engineering that is distinctly dealt by the theory of machines.In this way we are confronting a subject of instrumentation from electrical as well as mechanical perspectives. Moreover, this system is a device for the purpose of studying piezoresonse of ferroelectric materials in particular and ceramics in general.

What we are trying to make a point is that no subject is independent on itself for any discussion and hence converge to happen practically. Also, the use of microcontrollers and logic devices extends the scope of electronics and computer science into this scheme of a bigger picture revolving instrumentation for piezoresponse studies. Wu et. al. demonstrated the measurement of piezoelectric coefficients (d33 and e31,f) at various forces and frequencies and the vibrational resonance frequency of the piezoelectric response.

This compact piezoelectric coefficient measurement system has proved to be a versatile instrument for studying piezoelectric coefficients and their frequency dependence in a cost-effective way[150].

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Figure : Gear system arrangement clamped to a motor and transformer assembly Our proposed plan stands something like the figure below. Here we want to use the setup arranged with gears and motors for driving the piezo measurement mechanism. A continuous uniaxial pressure device enables the study of the piezoresistance and the pressure induced change in electrical properties of bulk samples [151]

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Figure : Schematic of the Piezoresponse measurement mechanism We had initially tried to press the gas lighter piezo with a hydraulic pressure gauge of our pellet maker. A couple of PCB copper cladding was cut into (0.0254x0.0254) m2 area and placed at the top and bottom of the piezo cylinder. A piece of wire was soldered into a small part of the copper cladding and connected to probes of a multimeter. This apparatus was placed under the pellet maker and the force was applied through the hydraulic pump.

The PCB pieces broke down for two and half stroke of the hydraulic pump. We also observed that there was damage to the piezomaterial, not just on the ends but also on the center. During this experimentation, we observed that there was a voltage spike of magnitude 329 V on the multimeter. Our experiments were unlikely to meet the challenges of piezoresponse measurement tools involving hydraulic pressure gauges before undergoing many trials. Kim et al. constructed an experimental setup for pneumatic loading method. This system was supplemented with a pressing probe for MTech. Nanoscience and Tech.

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delivering pneumatic pressure onto the film surface, a pressure gauge for the force or stress measurement, a charge amplifier for metering the electrical charge from the piezoelectric films, a vacuum pump or a compressor for the source of pneumatic power, and some valves for pneumatic control [152].

A direct piezoelectric potential measurement from a single PZT nanofiber was demonstrated by Chen et al. [153]. But our attention was caught by construction of the compressometer to study the effects of the stress on the dielectric and ferroelectric properties [154].

Figure : Rectangular gearbox arrangement We discovered that the speed of rotation of our pulleys is 3 times the speed of rotation of the drive gear. In simple terms, for every complete rotation of the central gear, the two side gears fixed to the pulley rotates 3 rotations.

Analysis Circuitry We came up with a system for analysis of piezo responses from the available electronic systems of sensors and actuators. Though we donâ&#x20AC;&#x2122;t have any simulation technique to verify its working, it was more of a fundamental knowledge to bring some working modules and assemble them to take advantage of modern day measurement tools though MTech. Nanoscience and Tech.

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precision to resolve the nanoscale effects of piezomaterials was left to the future researchers.

Figure : Schematic of modular assembly of analysis system We shall discuss each of the above parts in detail. Actually, there are generic steps for assembling these as stated by Hongping Hu et al. [129]. But we had alternative directives that inspired us to proceed with our method with many not-so-common elements to commence with.

Power Module Using ICs 7809 and 7805 voltage regulators, we conceptualized a model power supply regulator capable of outputting 9V and 5V DC with the transformer, a fuse and a metal cap packaged bridge rectifier with the rating of 4A. Here, in the figure below we show the arrangement that was realized using pre-holed PCB.

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Figure : Regulated Power supply for 5V and 9V

Figure : Front and back view of our designed power supply.

As we observe, our system demands that we have a 12V supply for the motor, 9V for microcontroller and 5V for logic gates and 3.3V for backlight of LCD. We forgot that our desired system doesnâ&#x20AC;&#x2122;t accommodate a 12V supply!

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Figure : Power supply with 12V,9V and 5V regulated power Another possible scheme we recommend is to put resistances at appropriate voltage levels and obtain the desired drive as shown in the scheme below:

Figure : Power supply with 12V regulated and the rest are just attenuated from the prior.

It is said that a motor often emanates a back electro motive force (emf) as there are coils that oppose the forming of a magnetic field within the device. As a method of precaution we went down to finding out that one way is to definitely advice for a regulator along with resistances for the above circuit; of course even optoisolators can do this functioning. We were not concerned with the unavailable 3.3 V as there were supply pins for 3.3V from Arduino microcontroller.

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Figure : Regulated power supply with all 12V,9V & 5V regulators.

We need to use the jack of a 9V pin like the one used for the mobile phone chargers, except in this case it may be slightly bigger one for the simplicity of holding (ergonomically termed â&#x20AC;&#x153;Human Power Gripâ&#x20AC;?). It simplifies connection to the Arduino.

Here is a simple circuit that can be used to test a crystal before using it in a circuit. The circuit is built around two BC547 transistors (T1 and T2) and a few discrete components. The oscillator circuit formed by transistor T1, resistors R1 and R2, and capacitors C1 and C2 oscillates if a good crystal is connected to the test points marked as CUT (crystal under test). The output from the oscillator is rectified by diode D1 and filtered by capacitor C3. The positive voltage appearing across the capacitor is fed to the base of transistor T2, causing it to conduct.

Figure : Power pins for 9V

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Figure : Prototype of the crystal tester

Testing of a crystal is simple: Insert the crystal at CUT points shown in the circuit diagram and press test switch S1. If LED1 glows, your crystal is good and you can use it in a circuit. We wish to use any piezomaterial for the quartz crystal tester. The position where the piezo is connected will be given to the top and bottom copper plate electrodes in our assembly, discussed in the previous section on mechanical developments.

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Figure : Schematic diagram of the electrical circuit of piezo tester The circuit is powered by a standard 9V battery. Push-to-on switch S1 is included to prolong the battery life but itâ&#x20AC;&#x2122;s not needed if you use a socket for the crystal under test.

Assemble the circuit on a general-purpose PCB and enclose in a suitable small cabinet.

Fix the two-pin connector, LED1 and test switch on top of the cabinet. Fix the 9V battery inside the cabinet. But here we plan to give it to the regulated power supply of 9V. Note. You can use 2N3563 transistors instead of BC547 [155] .We designed our prototype with the help of Kicad software and printed the silk screens on a transparent gloss sheet and transferred them by padding the PCB copper cladding with some cloth and ironing them and then exposed them to strong illumination by keeping it under a distilled water maker which heats the electrodes to brilliant red illumination.

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We have the ULN2003 driver IC for a 6 pin stepper motor along with a fuse also to defend against the back emf from destabilizing the system.

Figure : Driver circuit with ULN2003 IC for 6 pin stepper motor control.

We even have a small 4 wire stepper motor for the purpose of driving a small window to close it after the sample is put in the sample space and console is used to initiate the processing. For this stepper motor, we use a different driver.

Figure : Driver circuit with the L293D IC for 4 wire stepper motor control.

The use of heat sinks is another point to be noted as there will be significant power dissipation from the regulator ICs or any MOSFET used.

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Figure : Heat Sink The salient feature of our instrument is that the actuator is independent from either the charge generated or voltage developed as well as exhibit minimal influence on the external parameters of force sensor, though not electrically isolated in the consideration of entire system. Storage mechanism was ideally undertaken with a different unit altogether [156].

We use an Analog to Digital Converter to convert the analog voltage levels of the force sensor and the voltage levels of the top and bottom electrodes of the piezo response device we intend to construct. The ADC0808 and ADC0809 are monolithic CMOS devices with an 8-channel multiplexer, an 8-bit analog-to-digital (A/D) converter, and microprocessor-compatible control logic. The 8-channel multiplexer can be controlled by a microprocessor through a 3-bit address decoder with address load to select any one of eight single-ended analog switches connected directly to the comparator. The 8-bit A/D converter uses the successive-approximation conversion technique featuring a highimpedance threshold detector; a switched-capacitor array, a sample-and-hold, and a successive-approximation register (SAR). One method of addressing the digital ramp ADC’s shortcomings is the so-called successive approximation ADC. The only change in this design is a very special circuit known as a successive approximation register. Instead of counting up in binary sequence, this register counts by trying all values of bits starting with the most significant bit and finishing at the least significant bit. Throughout the count process, the register does the monitoring of the comparator’s output to see if the binary count is less than or greater than the analog signal input, adjusting the bit values accordingly. The way the register counts is identical to the “trail-and-fit” method of decimal-to-binary conversion, whereby different values of bits are tried from MSB to MTech. Nanoscience and Tech.

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LSB to get a binary number that equals the original decimal number. The advantage of this counting strategy is much faster results: the DAC output converges on the analog signal input in much larger steps than with the 0-to-full count sequence of a regular counter.

Also stepper motor rotations are finely resolved giving enough time for ADC to pass data and allow sequential logic system to recognize charge development simultaneously. The next phase is only calibration of force sensor to varying forces by placing standard weights on it and noting the ADC values that should be made part of a look-up table for microcontroller and identify time-lag with oscilloscope to place capacitors at input stage along with precision instrumentation amplifier with a real time clock (RTC) at the output stage for proper synchronization.

Figure : Force sensors The force sensor is actually the system intend to construct. As a small force sensor, it is an in-situ technique with fixed parameters inside that are difficult to process for real-time MTech. Nanoscience and Tech.

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data except for the output. Here we are bringing an ex-situ technique with calibrations to understand the parameter relationships of sample materials. Ground is a third line of wire connected to the base if it is a metal or otherwise not necessary. This should be brought out with the two wires of the transformer and combined in a wire sleeve to put into a 3A 3 pin plug.

Logic System Module We can make the logic systems for the custom logic we intend to bring out. The choice of MSI ICs is good enough to get our work done for multiplexing and decoding and may be sometimes encoding. Much work in this section is left out. Also there is consideration in incorporating FPGAs. The choice of ASIC vs. FPGA for volume production is on caseto-case basis. A field-programmable gate array (FPGA) can be purchased off-the-shelf and programmed by the user, whereas an application-specific integrated circuit (ASIC) is manufactured to a customerâ&#x20AC;&#x2122;s specification. This distinction has not changed since the dawn of both technologies yet, the performance offered by these two technologies, and the cost tagged on them, have dropped considerably over the years.

Arduino: The Numero Uno Prototyping Platform Arduino is a tool for making computers that can sense and control more of the physical world than our desktop computer. It's an open-source physical computing platform based on a simple microcontroller board, and a development environment for writing software for the board.

Arduino can be used to develop interactive objects, taking inputs from a variety of switches or sensors, and controlling a variety of lights, motors, and other physical outputs. Arduino projects can be stand-alone, or they can be communicated with software running on oneâ&#x20AC;&#x2122;s computer (e.g. Flash, Processing, MaxMSP.) The boards can be assembled by hand or purchased preassembled; the open-source IDE can be downloaded for free.

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The Arduino programming language is an implementation of Wiring, a similar physical computing platform, which is based on the Processing multimedia programming environment.

Why Arduino?

There are many other microcontrollers and microcontroller platforms available for physical computing. Parallax Basic Stamp, Netmedia's BX-24, Phidgets, MIT's Handyboard, and many others offer similar functionality. All of these tools take the messy details of microcontroller programming and wrap it up in an easy-to-use package.

Arduino also simplifies the process of working with microcontrollers, but it offers some advantage for teachers, students, and interested amateurs over other systems: •

Inexpensive - Arduino boards are relatively inexpensive compared to other microcontroller platforms. The least expensive version of the Arduino module can be assembled by hand, and even the pre-assembled Arduino modules cost less than $50.

•

Cross-platform - The Arduino software runs on Windows, Macintosh OSX, and Linux operating systems. Most microcontroller systems are limited to Windows.

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Simple, clear programming environment - The Arduino programming environment is easy-to-use for beginners, yet flexible enough for advanced users to take advantage of as well. For teachers, it's conveniently based on the Processing programming environment, so students learning to program in that environment will be familiar with the look and feel of Arduino

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Open source and extensible software- The Arduino software is published as open source tools, available for extension by experienced programmers. The language can be expanded through C++ libraries, and people wanting to understand the technical details can make the leap from Arduino to the AVR C programming language on which it's based. Similarly, you can add AVR-C code directly into your Arduino programs if you want to.

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â&#x20AC;˘

Open source and extensible hardware - The Arduino is based on Atmel's ATMEGA8 and ATMEGA168 microcontrollers. The plans for the modules are published under a Creative Commons license, so experienced circuit designers can make their own version of the module, extending it and improving it. Even relatively inexperienced users can build the breadboard version of the module in order to understand how it works and save money.

Figure : Arduino with Micro SD card shield.

Running out of memory space is never a problem in our Arduino project. The micro SD Shield of SparkFun equips our Arduino with mass-storage capability, so we can use it for data-logging or other related projects. This shield comes populated with a microSD socket, red power indicator LED, and a reset button; but it does not come with headers installed.

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We actually have another Indian made Arduino called Freeduino as well where the connection to the power from a regulator to the USB of computer meant that every time we have to manually switch over the jumper pin at the board power lines. Among the figures below, one was for 8 bit and the other was 32 bit address and data capability with ATMEGA 8 and ATMEGA 328 ICs incorporated.

Figure : Freeduino with Atmel 8 bit and 32 bit ICs Our prolonged attempt to get a connector for LCD to Arduino witnessed failures primarily due to the incompatibility of Arduino with LCD available to us, which is

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JHD162.

Figure : JHD 162 LCD with soldered pin jack The maker of the LCD was a Chinese and our Arduino was an Italian made. We didn’t attempt to buy from online store, which may be our biggest mistake. This caused us a fiasco of time and money investment over trying to get things compatible. One primary problem with the LCDs is that they have pins that don’t solder well with male connector pins. So we went for a jack type of a 16 pin connector with male and female. This had a strand of copper wires which posed difficulty of soldering with copper on PCB. Hence we established a separate module for the sole purpose of getting connections for LCD to Arduino. One major reason why we went for the Arduino is because it is having many digital pins, which can produce pulse width modulation signals that help control motor’s directionality. Even a Rasberry Pi or 8051 or beagle board can’t do motor directing and adding an Arduino might be an option even there.

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Figure : Connector module for an LCD tp Arduino

Figure : Modified connectors to LCD to better the connectivity of pins Our final system looks somewhat as follows. It consists of a casing that houses the mechanical and electronic systems with only the display acting a visual aid with a console. Also, we can add a recorded message in the micro SD card and play it on a small speaker as an effecting interactive message system. There can be a push button mechanism to initiate the system and stop the system. One of the switches will be from the transformer. There can a PLD switching also. Yet, the most basic means of switch is the lift-up switch.

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Figure : Casing that houses the gear mechanism for the mechanical and electronic systems. *********

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RESULTS AND DISCUSSION XRD Comparisons

(b)XRDofofthe Gas lighter piezo (a)XRD synthesized Pb Zr 0.52 Ti 0.48 O 3 under various

Figure : XRD for synthesized PZT and that of a gas lighter piezo

X-ray diffraction studies from the samples of the various synthesized lead Zirconate titanates were analysed for some of the samples listed in the observation of the experimentation. We observe that the crystalline phases of the samples prepared from the hydrothermal methods of synthesis interpret the same phase planes that are parallel to the faces of the crystals. They all have sharp crystallinity as same planes appear in all the XRD peaks of the samples and so also with the use of EDTA. The data is obtained at University of Mysore with RigaKu Miniflex II Desktop X-Ray Diffractometer. Then we broke down a house-hold gas lighter for determining their piezo material. This pattern resembles the formation of a single phase of a nanocrystalline product in the work of A. Fernรกndez et al., which was identified as that of the perovskite structure of Pb (Zr0.52Ti0.48)O3, where all diffraction peaks can be perfectly indexed to the tetragonal structure (JCPDS card 33-0784), these results are consistent with those reported in the literature for this composition. In order to determine the average crystallite size, a peak broadening method was applied using the classical Scherrer-Warren equation over the [1 1 1] and [2 0 0] reflections [157].

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We even cut a piezo crystal oscillator device of 1MHz and saw the quartz placed in the electrode spacing. Some limitation in replacing piezoelectric crystals (quartz, LiNbO 3, etc.) with piezoceramics are due to difficulties in obtaining piezoceramics exhibiting repeatability of parameters, small temperature and time stability of these parameters, strong non-linear phenomena, strong damping of ultrasonic waves, etc. Most of the mentioned shortcomings follow from the nature of piezoceramics, which is connected with the technology of their fabrication [158].

We noticed that the piezo material in gas lighter was a ceramic from the moment we recognized that they were porous and that upon using a plier and damaging it, it became vitreous powder just like mud. So we went ahead to find if the XRD was able to tell that the structure was well ordered. So we sent the same to Indian Institute of science. With the help of Dr C Shivakumara, we got our XRD of Figure (b) from X-ray Diffractometer: Phillips (with Xâ&#x20AC;&#x2122;lerator detector) located at SSCU of IISc. There seem to be a perfect match with the data of the synthesized PZT. However, even finer details was sought after to interpret the process of poling that had taken place and revealing of the domain alignment inside the gas lighter piezo. The results of the data are yet to be obtained. These piezo materials were charred and we suspect that they were even sintered in an unusually high temperature. The XRD patterns of both the figures confirm that they are perovskites. Under the conditions of sintering, of amorphous nano powders, Z. Surowiak et al. obtained fine-grained piezoceramics. It was found by W. Thamjaree et al. that an increase of the annealing

temperature

caused

the

microstrain to decrease owing to an increase in particle size. The Scherer formula used to calculate the particle size yielded considerably smaller values [159]. From the inspection the work of N. S. Gajbhiye et al. [29], our XRD results coincide with those of the JCPDS file No.50.0346.

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Figure : Gas lighter internals and piezo cylinders

We carried out a range of sintering techniques for our synthesized PZT. At first the material was made into pellets and this was sent to sintering at IISc, Bangalore. We calculated that the thickness of the material was not quite dense as to withstand sintering which happen to be 1.46589E-08 meters. But we were surprised to find that there were two surviving samples after this process. From empirical data observations and qualitative analysis we found that among the two, H16 was the best. So we iteratively carried out synthesis for this sample and we found that repeating the same composition, the morphology of the end product was not the same at every single instance. There are instances where studies on sintering effects with Niobium doping proved to be essential for improving dielectric and piezoelectric properties [167] though doping was left as future considerations in our work.

Figure : Quantiitative compositional distribution of the sample H16

UV-Visible Spectrum.

After 4 hours in furnace and cooled for a 11 hours, we performed a UV visible spectroscopy of the solid solution after the reaction was completed inside the teflon cup in order to determine if there were possibilities that any nanosized residues trickling down the conical flask could have capability to seep into the layers of micro porous filter paper. The UV-Visible machine we used was UV Visible spectrometry with Spectra Suite from Ocean Optics.

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U V visible spectra of PZT solid solution 1.8

T(lab) = 28.5 0C Humidity = 56.5%

422.97, 1.514

1.6 1.4 1.2 1

tin rp so b A

0.8 0.6 0.4 0.2 0 270

370

470

570

670

770

870

970

1070

1170

1270

Wavelength in nm

Figure : UV Visible Spectroscopy of the solid solution of PZT The UV visible spectra revealed that there was lot of noise between heavy elements, which happens to be lead in our case. The spectrum was taken with distilled water as standard reference. We have not yet established the band gap measurements [67].

SEM Ananlysis Earlier, we had the FESEM images of the PZT from IISc. They were synthesized with random sample numbers but we maintained the 52:48 as the standard combination. Stable tetragonal single perovskite phase was obtained by N S Gajbhiye et al. and the high resolution SEM there, revealed presence of non-agglomerated, uniformly distributed and spherical nanoparticles of PZT [29]. Our FESEM images tell that our perovskites are monodisperse and have resemblance to flakes. These macroscopic techniques are only suitable for materials where the crystallography is preserved throughout the sample. In fine-grained polycrystalline and nanostructured materials, for example, where the size of crystallographically varying regions is beyond the resolution of the measurement technique, the orientation cannot be ascertained in order to quantify the piezoresponse [160].

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Figure : FESEM image for PZT (52:48).

Piezoelectricity measurements A gas lighter was dismantled and the piezo element was recovered. This material was fixed with a PCB copper cladding of 25.4 sq. mm, and soldered to a wire of single strand on both the top and bottom and placed inside a small cardboard box of a volume of 25.4 cubic mm with a hole to allow the wire to come out. It was then loaded with a spring on top and a plastic plate of thickness 0.8 cm and area of 10 sq. cm was put over it and this set-up was placed inside a hallow cardboard box of dimension 10 sq. cm base and a height that was cut to an extent of just letting the plastic surface and the edges of the cardboard are even. The cardboard was again MTech. Nanoscience and Tech.

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holed and the wires were taken out and wounded tightly on the leads of a multimeter. Thanks to the proprietor of Shri Siddeshwara General Stores, Shankaraghatta, Shimoga, Mr C V Hiriyonnaiah, we procured weight stones of uneven masses and put them over the plastic plate and obtained the piezo responses of the gas lighter piezo. This was the Akai gas lighter piezo, we tested on. The voltages were only instantaneous. We recorded on only the first trail readings, though more trails would have yielded greater accuracy.The voltages were rising initially as the weights are put on the plastic plate and subsided to zero once it went into rest.

No sooner we lift the weight, again, the voltages rise from zero value and go on high and subside to zero than when the weight is off the plastic plate. We recorded only the instantaneous peak value of the DC voltage as seen on multimeter.

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Impedance Spectroscopy Analysis Sintering of PZT at high temperatures results in loss of Pb unless an ambient Pb activity is maintained. The tell-tale sign of Pb loss is an increased conductivity, usually manifested in unacceptably high values of tan δ. The conductivity is caused by oxygen vacancies and/or electron holes which are a by-product of Pb evaporation [161]. We made a study on the conductivity over cycling the electric field intensity with varying frequency before carrying out sintering to further take on a comparative study.

Figure : Conductivity test of PZT sample H15 We notice that there is a sharp fall in conductivity before the sample excites for the applied electric field intensity. This is indicative of the dipole rearrangements for the unpoled sample.

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Further explanations are required to explain the internal morphological changes with in-situ analysis.

Dielectric Measurements Dielectric properties were studied as a function of frequency and temperature were undertaken

by N. S. Gajbhiye et al. [29]. The ferroelectric phase in the prepared PZT is stable up to 4750C(Tc) as revealed from the dielectric constant vs. temperature plot. Dielectric constant and losses were measured in the temperature range 30 â&#x20AC;&#x201C; 5000C at various frequencies. The studies revealed a high dielectric constant of 390 and dielectric loss of 0.059 at room temperature [29].

Figure : Frequency dependent behaviour of dynamic permittivity So we went to do the dielectric measurements as well except with a change. Our studies mainly required to identify the number of the compression and expansions that the synthesized PZT can undergo before needing serious replacements. So we measured the dielectric constant against the applied frequency of the electric field. From our knowledge of the tensors associated with the domain orientations of PZT, the electric and mechanical forces were interchangeable. Further work could involve simulation of mechanical stresses and determination of electric field intensities. Also the possibilities of dielectric measurements for MTech. Nanoscience and Tech.

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the same parameters could be done for other samples along with other parameters involved in literatures.

A. Fernandez-Osorio et al. obtained curves for the frequency dependence of the dynamic parameter ε/(ω). At low frequencies there is a strong dispersion, but as the frequency increases ε/(ω) tends to be frequency independent. The magnitude of ε/(ω) depends slightly on the temperature. Then, finally there is no doubt on the existence of a transition temperature, although it seems to be dispersive in character. Regarding this last point, the material behaves as if it were constituted by a set of nano-ferroelectric grains, where ferroelectric domains would have a slightly different Tc. In there, it seems to be difficult to classify the material behaviour as it were a relaxor, since there are difficulties to prove that Curie-Weiss law fails or the maximum on the ε/(ω)vs. T curves is frequency dependent [162].

M. K. Cheung et al. had a figure of the relative permittivity (ε r) and dielectric loss (tan δ) of the composite films as functions of frequency. Because of the porous structure, the observed ε r value of one of their samples becomes much smaller than that of a sol-gel derived PZT film. At the same time the observed tan δ magnifies in the frequency range of 100 Hz to 100 kHz. On the other hand, the observed ε r of the dense composite film, is rather high, while the observed tan δ value is insignificant in the whole frequency range [163]. S.-Y. Chu et al. performed some doping with Nb and the dielectric constant measured at 1 kHz is about 1500 and the loss factor is smaller than 2%. It showed that the Nb additives were helpful to improve both the dielectric and piezoelectric properties [164]. Thus we are lead to promote Nb doping in our future studies.

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Conclusion The synthesis of lead zirconate titanate (PZT) by hydrothermal method has been successful. The samples with characterized and confirmed that perovskite structure is retained. The development of a standalone instrument for testing piezoelectric properties of PZT is proposed. The salient feature of proposed our instrument is that the actuator is independent from either the charge generated or voltage developed as well as exhibit minimal influence on the external parameters of force sensor, though not electrically isolated in the consideration of entire system. Running out of memory space is never a problem in our Arduino project with micro SD card shield enabling external memory limited to memory card storage volume. **********

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Future Work The synthesized material is still to be processed by sintering and poling as described in the literature. Various elemental doping of PZT is to be undertaken as studies as cases. After that, the materials need to be tested for their mechanical properties. In the instrumentation section, the assembly of the above said parts was partially carried out in the limited span of semester. A casing of aluminium is to be fabricated. Further work involves attaching bigger gears instead of small gears in the rectangular gear box. This will further bring down the speed of the system to allow for practical calibration of the measurement system with finer resolution. Currently SD card provides a provision to store data. It can be extended to include recorded messages to aid in the accessibility of the console system. The console is not developed nor described. This part of the work is purely an electronic design arena. It involves 4x4 key pad or a PLD. Our preference would suggest that a key pad would suffice for the user accessibility in addition to LCD even at the advanced stages. A large number of mechanical properties for study is on due.

A lot of calculations for spring and wire rope are to be done [165] the regulated power supply and the logic system is to be configured and simulated. This model has to be designed and constructed on a PCB. Again, there will be time when an entire OS would be needed to operate the instrument alongside a computer. Then, Rasberry Pi has to be introduced along with Arduino. A schematic of an energy harvester using PZT has been invented by Hu et al. [166] which is what our future storage must be constitute of with some additional experimenting with structural stability.

INDEX

A Arduino, 83

K Kicad, 80

B Burns temperature, 64

L low temperature cofired ceramic (LTCC), 55

C

M

coercive field, 3, 20, 37, 41, 42, 44, 46, 47, 50, 57, 60

magnetic coupling, 19

compressometer, 76

mechanical quality factor, 55

Curie temperature, 8, 12, 32, 42, 50, 58

micro crack, 56 microstrain, 91

D dielectric constant, 20, 32, 38, 43, 46, 52, 57, 95, 96, 97 dielectric loss tangent, 57

monodisperse, 93 morphotropic phase boundary, 36 Multifunctional piezoelectric systems, 61

N

E nanofiber, 75

EDTA, 32

nanofibers, 64

EDTA complexation, 31 effective electromechanical coupling factor, 55

F

nanogenerator, 64 nanoindenter, 61 nanoshell, 15

O

ferroeleasic switching, 42 ferroelectric, 32

optoisolators, 78

flexoelectricity, 55

P

G paraelectric, 32

Green Chemistry, 31

Piezoelectricity, 55

H hydrothermal, 30

R relaxor, 40, 64, 96 remnant polarization, 2, 6, 20, 28, 41, 42, 49, 50, 57, 63

S Solution pH, 35

U UV-Vis-NIR spectrophotometer, 38

steric effect, 34

V

stress corrosion cracking (SCC), 58 supersaturation, 33

vibrometer, 54 viscoplastic, 56