Showing papers on "Lead zirconate titanate published in 2004"

Thin Film Piezoelectrics for MEMS

Abstract: Thin film piezoelectric materials offer a number of advantages in microelectromechanical systems (MEMS), due to the large motions that can be generated, often with low hysteresis, the high available energy densities, as well as high sensitivity sensors with wide dynamic ranges, and low power requirements This paper reviews the literature in this field, with an emphasis on the factors that impact the magnitude of the available piezoelectric response For non-ferroelectric piezoelectrics such as ZnO and AlN, the importance of film orientation is discussed The high available electrical resistivity in AlN, its compatibility with CMOS processing, and its high frequency constant make it especially attractive in resonator applications The higher piezoelectric response available in ferroelectric films enables lower voltage operation of actuators, as well as high sensitivity sensors Among ferroelectric films, the majority of the MEMS sensors and actuators developed have utilized lead zirconate titanate (PZT) films as the transducer Randomly oriented PZT films show piezoelectric e(31, f) coefficients of about - 7 C/m(2) at the morphotropic phase boundary In PZT films, orientation, composition, grain size, defect chemistry, and mechanical boundary conditions all impact the observed piezoelectric coefficients The highest achievable piezoelectric responses can be observed in {001} oriented rhombohedrally-distorted perovskites For a variety of such films, e(31,f) coefficients of - 12 to - 27 C/m(2) have been reported

Lead Free Piezoelectric Materials

Abstract: Lead oxide based ferroelectrics, represented by lead zirconate titanate (Pb(Zr, Ti)O3) or PZT) are the most widely used materials for piezoelectric actuators, sensors and transducers due to their excellent piezoelectric properties. Considering lead toxicity, there is interest in developing piezoelectric materials that are biocompatible and environmentally friendlier. The low density of non-lead based materials can also be an advantage in transducers for underwater and medical imaging due to expected lower acoustical impedance. Another impetus for seeking alternative to lead based compositions is the need for piezoelectric materials for operation at high temperatures. Several classes of materials are now being reconsidered as potentially attractive alternatives to PZT for special applications. The potassium niobate family, KNbO3, exhibits low dielectric constants, large thickness coupling coefficient along certain non-polar directions, and low density, all of which have advantages for high frequency transducer applications. Several compositions belonging to bismuth titanate family, Bi4Ti3O12, such as SrTi4Bi4O15, are promising candidates for high temperature applications. Lead free materials alone (eg. (Na0.5Bi0.5)TiO3) or in solution with PT (BiScO3 – PbTiO3) are also potentially interesting as they combine high piezoelectric activity and, in some cases, relatively high T c . For these families of piezoelectric materials, the processing and piezoelectric response under different conditions of pressure, frequency, and temperature are presently much less understood than for the classical lead containing systems. In this presentation we review and discuss piezoelectric properties of selected lead free compositions (principally for members of the potassium niobate family and bismuth titanate layered compounds) in relation to structural and microstructural features as well as extrinsic contributions (domain walls displacement, conductivity) to their electromechanical properties. It is shown that it is possible to obtain remarkably stable piezoelectric response in some compositions, while others exhibit strong dependence of piezoelectric properties on driving field and frequency. Origins of these different behaviours are discussed.

Temperature dependence of the piezoelectric response in lead zirconate titanate films

Abstract: The temperature dependence of the effective transverse piezoelectric coefficient (e31,f) in lead zirconate titanate (PZT) thin films was measured between −55 and 85 °C. e31,f was calculated by simultaneously monitoring the piezoelectric charge output and strain in the film during wafer flexure. This method was used to characterize the temperature dependence of e31,f in PZT films with 2, 4, and 6 μm thickness and 40/60, 52/48, and 60/40 Zr/Ti ratios. |e31,f| was found to increase with temperature and average increases were 46%, 32%, and 12% for films with PZT 60/40, 52/48, and 40/60 compositions, respectively. Measurement uncertainty ranged from ±3%–12%. The measured temperature dependences of e31,f were consistent with the rapid rise in intrinsic d31 as Tc is approached, suggesting that they were controlled by intrinsic contributions. Additional contributors to the measured variation in the PZT film piezoelectric response over the measured temperature range were identified. Changes in film elastic propert...

The morphotropic phase boundary and dielectric properties of the xPb(Zr1∕2Ti1∕2)O3-(1−x)Pb(Ni1∕3Nb2∕3)O3 perovskite solid solution

Abstract: The solid solution between the normal ferroelectric Pb(Zr1∕2Ti1∕2)O3 (PZT) and relaxor ferroelectric Pb(Ni1∕3Nb2∕3)O3 (PNN) was synthesized by the columbite method. The phase structure and dielectric properties of xPZT-(1−x)PNN where x=0.4–0.9 and the Zr∕Ti composition was fixed close to the morphotropic phase boundary (MPB) were investigated. With these data, the ferroelectric phase diagram between PZT and PNN has been established. The relaxor ferroelectric nature of PNN gradually transformed towards a normal ferroelectric state towards the composition 0.7PZT-0.3PNN, in which the permittivity was characterized by a sharp peak and the disappearance of dispersive behavior. X-ray diffraction analysis demonstrated the coexistence of both the rhombohedral and tetragonal phases at the composition 0.8PZT-0.2PNN, a new morphotropic phase boundary within this system. Examination of the dielectric spectra indicates that PZT-PNN exhibits an extremely high relative permittivity near the MPB composition. The permittivity shows a shoulder at the rhombohedral to tetragonal phase transition temperature TRT=195°C, and then a maximum permittivity (36 000 at 10kHz) at the transition temperature Tmax=277°C at the MPB composition. The maximum transition temperature of this system was 326°C at the composition x=0.9 with the relative permittivity of 32 000 at 10kHz.

Anomalous Power Law Dispersions in ac Conductivity and Permittivity Shown to be Characteristics of Microstructural Electrical Networks

Abstract: The frequency dependent ac conductivity and permittivity of porous lead zirconate titanate ceramic with the pore volume filled with water are shown to match the simulated electrical response of a large network of randomly positioned resistors and capacitors. Anomalous power law dispersions in conductivity and permittivity are shown to be an electrical response characteristic of the microstructural network formed by the porous lead zirconate titanate pore structure. The anomalous power law dispersions of a wide range of materials are also suggested to be microstructural network characteristics.

Synthesis and piezoresponse of highly ordered Pb(Zr0.53Ti0.47)O3 nanowire arrays

Abstract: We report the synthesis and characterization of ferroelectric lead zirconate titanate PbsZr0.53Ti0.47dO3 (PZT) nanowires. The PZT nanowires, with diameters of about 45 nm and lengths of about 6 mm, were fabricated by means of a sol-gel method utilizing nanochannel alumina templates. After postannealing at 700 ° C, the PZT nanowires exhibit a polycrystalline microstructure, and x-ray diffraction and transmission electron microscopy study revealed their perovskite crystal structure. The piezoelectric characteristics of individual PZT nanowires were demonstrated by piezoresponse force microscopy. © 2004 American Institute of Physics .

A high energy synchrotron x-ray study of crystallographic texture and lattice strain in soft lead zirconate titanate ceramics

Abstract: The lattice parameters and crystallographic texture in La, Sr-doped soft lead zirconate titanate ceramics were examined using high-energy synchrotron x-ray diffraction. The preferred orientations in poled tetragonal and rhombohedral ceramics near the morphotropic phase boundary, caused by ferroelectric domain switching, were determined by monitoring the (002)∕(200) and (111)∕(111¯) intensity ratios, respectively. The lattice strains were also monitored using the {111} and {200} plane spacings in tetragonal and rhombohedral ceramics, respectively. The diffraction experiments were carried out in transmission, enabling the true “bulk” state to be characterized. It was observed that for the tetragonal phase both the lattice spacing d{111} and the intensity ratio R{200} varied linearly as a function of sin2Ψ,Ψ being the angle between the plane normal and the macroscopic polar axis. Similar observations were made for d{200} and R{111} in rhombohedral ceramics. The results are interpreted in terms of the remanen...

Frequency dependence of magnetoelectric interactions in layered structures of ferromagnetic alloys and piezoelectric oxides

Abstract: Magnetoelectric (ME) interactions in layered structures of magnetostrictive and piezoelectric phases are mediated by mechanical deformation. Here we discuss the frequency dependence of ME coupling in bilayers and trilayers of Permendur, a ferromagnetic alloy, and lead zirconate titanate. Data on ME voltage coefficient versus frequency profiles reveal a giant ME coupling at electromechanical resonance. The maximum voltage coefficient of 90 V/cm Oe is three orders of magnitude higher than low-frequency values. The ME interactions for transverse fields are an order of magnitude stronger than for longitudinal fields. These results are in agreement with theory. The resonance ME effect, therefore, is a novel tool for enhancing the magnetic-to-electric field conversion efficiency in the composites.

Growth of Oxide Nanorod Arrays through Sol Electrophoretic Deposition

Abstract: Metal oxides, particularly complex metal oxides, are important materials for various applications in industry and technology. This is due to their multi-faceted functional properties, their chemical and thermal stability, and their mechanical properties. Metal oxides (and particularly complex metal oxides) can have many unique physical properties including electronic and ionic conductivity, superconductivity, ferroelectricity, piezoelectricity, dielectric and magnetic properties [1]. These materials find a wide range of applications in electronic devices, sensors and actuators. For example, piezoelectrics (typically lead zirconate titanate, PZT) play a key role in many micro electro-mechanical systems (MEMS) [2]. Tin oxide doped indium oxide (ITO) films on glass substrates have been widely used as optically transparent electrodes in devices such as light-emitting diodes [3]. Sol—gel derived mesoporous titania films are being intensively studied in inorganic—organic hybrid photoelectrochemical cells [4]. Further, many of the physical properties of oxide materials are tunable through appropriate doping or substitution [5]. Zirconia that is partially stabilized through doping with materials such as calcium oxide or yttrium oxide exhibits excellent mechanical properties, particularly toughness not commonly found in other oxide materials [6]. Doped zirconia is also an excellent oxygen ionic conductor, with applications in oxygen sensors and solid oxide fuel cells (SOFC) [6]. Oxide surfaces can have special chemical properties, making them useful as catalysts and sensors [7]. Furthermore, oxide surfaces can be easily incorporated with organic functional groups through surface condensation or self-assembly [8].

Magnetoelectric interactions in hot-pressed nickel zinc ferrite and lead zirconante titanate composites

Abstract: The synthesis by hot pressing and wide-band (10Hz–1MHz) magnetoelectric (ME) characterization of bulk composites of nickel zinc ferrite Ni1−xZnxFe2O4 (NZFO) (x=0–0.5) and lead zirconate titanate (PZT) are reported. Hot-pressed samples show an order of magnitude improvement in ME voltage coefficient compared to sintered samples. Frequency dependence of ME coefficients show a three order of magnitude enhancement at electromechanical resonance. The ME coupling is maximum for samples with equal volume of ferrite and PZT. The strongest ME interactions are measured for samples of NZFO (x=0.2) and PZT.

Synthesis of lead zirconate titanate nanofibres and the Fourier-transform infrared characterization of their metallo-organic decomposition process

Abstract: We have synthesized Pb(Zr0.52Ti0.48)O3 fibres with diameters ranging from 500 nm to several microns using electrospinning and metallo-organic decomposition techniques (Wang et al 2002 Mater. Res. Soc. Symp. Proc. 702 359). By a refinement of our electrospinning technique, i.e. by increasing the viscosity of the precursor solution, and by adding a filter to the tip of the syringe, the diameter of the synthesized PZT fibres has been reduced to the neighbourhood of 100 nm. The complex thermal decomposition was characterized using Fourier-transform infrared (FTIR) spectroscopy and x-ray diffraction (XRD). It was found that alcohol evaporated during electrospinning and that most of the organic groups had pyrolysed before the intermediate pyrochlore phase was formed. There is a good correspondence between XRD and FTIR spectra. We also verify that a thin film of platinum coated on the silicon substrate catalyses the phase transformation of the pyrochlore into the perovskite phase.

Experimental investigation into the effect of substrate clamping on the piezoelectric behaviour of thick-film PZT elements

Abstract: This paper details an experimental investigation of the clamping effect associated with thick-film piezoelectric elements printed on a substrate. The clamping effect reduces the measured piezoelectric coefficient, d33, of the film. This reduction is due to the influence of the d31 component in the film when a deformation of the structure occurs, by either the direct or indirect piezoelectric effect. Theoretical analysis shows a reduction in the measured d33 of 62%, i.e. a standard bulk lead zirconate titanate (PZT)-5H sample with a manufacturer specified d33 of 593pC/N would fall to 227.8pC/N. To confirm this effect, the d33 coefficients of five thin bulk PZT-5H samples of 220µm thickness were measured before and after their attachment to a metallized 96% alumina substrate. The experimental results show a reduction in d33 of 74% from 529pC/N to 139pC/N. The theoretical analysis was then applied to existing University of Southampton thick-film devices. It is estimated that the measured d33 value of 131pC/N of the thick-film devices is the equivalent of an unconstrained d33 of 345pC/N.

Resonance magnetoelectric effect in bulk composites of lead zirconate titanate and nickel ferrite

Abstract: Magnetoelectric (ME) Pb(Zr0.52Ti0.48)O3 (PZT)–NiFe2O4 bulk composites with various PZT volume fractions were prepared. The ME coupling coefficient, impedance, and flux density versus the frequency were measured. The magnetic bias and PZT volume fraction in the composites are investigated to optimize the ME output. It is revealed that ME resonances are caused by electromechanical resonance in the piezoelectric phase and magnetomechanical resonance in the magnetostrictive phase. Maximum magnetoelectric voltage coefficient resonance values of 6.7 V/cm Oe at 132.6 kHz and 6.12 V/cm Oe at 427.2 kHz for the composite with optimized PZT volume fraction of 0.55 were obtained at optimized magnetic bias of 0.6 kOe.

Effect of Poling Direction on R-Curve Behavior in Lead Zirconate Titanate

Abstract: R-curves of lead zirconate titanate (PZT) have been measured with compact tension (CT) specimens for different poling conditions and grain sizes. Depending on poling direction the plateau value of the R-curves ranged from 1.13 to 1.54 MPa·m1/2 for a grain size of 6.4 μm and from 1.14 to 1.30 MPa·m1/2 for a grain size of 5.2 μm. 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.

Piezoelectric thick bismuth titanate/lead zirconate titanate composite film transducers for smart NDE of metals

Abstract: Thick film piezoelectric ceramic sensors have been successfully deposited on different metallic substrates with different shapes by a sol?gel spray technique. The ball-milled bismuth titanate fine powders were dispersed into PZT solution to achieve the gel. The films with desired thickness up to 200??m have been obtained through the multilayer coating approach. These thick films were also effectively coated onto thin sheet metals of thickness down to 25??m. Self-support films with flat and shell geometries were made. Piezoelectricity was achieved using the corona discharge poling method. The area of the top silver paste electrode was also optimized. The center frequencies of ultrasonic signals generated by these films ranged from 3.6 to 30?MHz and their bandwidth was broad as well. The ultrasonic signals generated and received by these ultrasonic transducers (UTs) operated in the pulse/echo mode had a signal to noise ratio more than 30?dB. The main advantages of such sensors are that they (1) do not need couplant, (2) can serve as piezoelectric and UT, (3) can be coated onto curved surfaces and (4) can operate up to 440??C. The capability of these thick film UTs for non-destructive evaluation of materials at 440??C has been demonstrated.

Lead Zirconate Titanate Thin Films on Base-Metal Foils: An Approach for Embedded High-Permittivity Passive Components

Abstract: An approach for embedding high-permittivity dielectric thin films into glass epoxy laminate packages has been developed. Lead lanthanum zirconate titanate (Pb0.85La0.15(Zr0.52Ti0.48)0.96O3, PLZT) thin films were prepared using chemical solution deposition on nickel-coated copper foils that were 50 μm thick. Sputter-deposited nickel top electrodes completed the all-base-metal capacitor stack. After high-temperature nitrogen-gas crystallization anneals, the PLZT composition showed no signs of reduction, whereas the base-metal foils remained flexible. The capacitance density was 300–400 nF/cm2, and the loss tangent was 0.01–0.02 over a frequency range of 1–1000 kHz. These properties represent a potential improvement of 2–3 orders of magnitude over currently available embedded capacitor technologies for polymeric packages.

Three-dimensional high-resolution reconstruction of polarization in ferroelectric capacitors by piezoresponse force microscopy

Abstract: A combination of vertical and lateral piezoresponse force microscopy (VPFM and LPFM, respectively) has been used to map the out-of-plane and in-plane polarization distribution, respectively, of (111)-oriented Pb(Zr,Ti)O3-based (PZT) ferroelectric patterned and reactively-ion-etched capacitors. While VPFM and LPFM have previously been used to determine the orientation of the polarization vector in ferroelectric crystals and thin films, this is the first time the technique has been applied to determine the three-dimensional polarization distribution in thin-film capacitors and, as such, is of importance to the implementation of nonvolatile ferroelectric random access memory. Sequential VPFM and LPFM imaging have been performed in poled 1×1.5 μm2 PZT capacitors. Subsequent quantitative analysis of the obtained piezoresponse images allowed the three-dimensional reconstruction of the domain arrangement in the PZT layers of the capacitors. It has been found that the poled capacitors, which appear as uniformly p...

Nanowire transistors with ferroelectric gate dielectrics: Enhanced performance and memory effects

Abstract: Integration of ferroelectric materials into nanoscale field-effect transistors offers enormous promise for superior transistor performance and also intriguing memory effects. In this study, we have incorporated lead zirconate titanate (PZT) into In2O3 nanowire transistors to replace the commonly used SiO2 as the gate dielectric. These transistors exhibited substantially enhanced performance as a result of the high dielectric constant of PZT, as revealed by a 30-fold increase in the transconductance and a 10-fold reduction in the subthreshold swing when compared to similar SiO2-gated devices. Furthermore, memory effects were observed with our devices, as characterized by a counter-clockwise loop in current-versus-gate-bias curves that can be attributed to the switchable remnant polarization of PZT. Our method can be easily generalized to other nanomaterials systems and may prove to be a viable way to obtain nanoscale memories.

Electrical properties of piezoelectric sodium-potassium niobate

Abstract: Piezoelectric material is one of the most important components of the micro-electro mechanical system (MEMS). Most piezoelectrics have useful multi-functions for MEMS, e.g. sensor, actuator and transducer. An AFM cantilever, scanning mirror device and pumping system for a micro-chamber, are the typical applications of piezoelectric material on MEMS. Lead-based materials, e.g. lead zirconate titanate and lead lanthanum zirconate titanate, have been most popular among many piezoelectric materials. Recently alkali oxide materials, including potassium sodium niobate, have been given attention in view of their ultrasonic application and also as promising candidates for a piezoelectric non lead-based system. But this material system has been reported difficult to sinter only in the conventional method and it is possible to sinter by use of the hot isostatic press (HIP) method. In this report the synthesis process is, however, limited to the conventional solid state reaction method for the wide use of this material system. Several kinds of impurity doping into the base material is carried out in the sample preparation procedure. The physical, electrical properties and crystal structure of the several kinds of sodium-potassium niobate materials will be shown.

Method for Obtaining the Full Set of Linear Electric, Mechanical, and Electromechanical Coefficients and All Related Losses of a Piezoelectric Ceramic

Abstract: A method based on the use of four piezoelectric resonances for three sample geometries is presented that allows one to obtain all the dielectric permittivities, compliances, and piezoelectric coefficients of a piezoelectric ceramic in complex form and, therefore, all related losses. Piezoelectric losses are responsible for heat generation and hysteresis in actuators. The method is applied to a Navy type II PZT-based piezoelectric ceramic (PZT = lead zirconate titanate), for which the full set of linear electric, mechanical, and electromechanical coefficients is given in complex form. Full sets of coefficients for the available piezoceramics are required for exploiting all the possibilities of finite element analysis, both in fundamental research (mechanisms of degradation) and in development (element design). This numerical technique is necessary to explore arbitrary shapes provided by solid free-form-fabrication technologies.

Microstructural studies of (PbLa)(ZrTi)O3 ceramics using complex impedance spectroscopy

Abstract: Lanthanum modified lead zirconate titanate (PLZT:8∕60∕40) ceramics prepared by a sol-gel route showed a well-defined microstructure comprising of grains separated by boundaries. Complex impedance spectroscopy has provided a convincing evidence for the existence of both grain (bulk) and grain-boundary effects that were separated in the frequency domain in impedance spectrum. The impedance analysis further provided the value of relaxation frequency, which was a characteristic intrinsic property of the material and was independent of sample geometrical factors. Relaxation frequency calculated at different temperatures was used to evaluate bulk dielectric constant (eb), which was compared with the real part of the dielectric constant (e′). The temperature variation of the bulk electrical conductivity (σdc) indicated an evidence of Arrhenius-type thermally activated process showing a linear variation up to a temperature of 713°K and was predominantly governed by grain boundary conduction showing a plateau regi...

Structural and magnetoelectric properties of MFe2O4–PZT (M = Ni,Co) and Lax(Ca,Sr)1-xMnO3–PZT multilayer composites

Abstract: Thick-film layered magnetoelectric composites consisting of ferromagnetic and ferroelectric phases have been synthesized with nickel ferrite (NFO), cobalt ferrite, La07Sr03MnO3 (LSMO), or La07Ca03MnO3 (LCMO) and lead zirconate titanate (PZT) Structural, magnetic, and ferromagnetic resonance characterization shows evidence for defect-free ferrites, but deterioration of manganite parameters The resistivity and dielectric constants are smaller than expected values The magnetoelectric effect (ME) is stronger in ferrite–PZT than in manganite–PZT The ME voltage coefficient αE at room temperature is the highest in NFO–PZT and the smallest for LCMO–PZT The transverse ME effect is an order of magnitude stronger than the longitudinal effect The magnitude of αE correlates well with magnetic permeability for the ferrites

Demonstration and characterization of PZT thin-film sensors and actuators for meso- and micro-structures

Abstract: Recent development of next-generation medical devices, such as endoscopes and hearing aids, call for PZT (lead zirconate titanate oxide) thin-film sensors and actuators with thickness in the range of 1–30 μm to enhance actuation strength and sensor sensitivity. Currently, sol–gel derived PZT films often have thickness less than 0.2 μm per coating. Moreover, thermal stresses in the films limit the crack-free area to less than 1 mm2. This paper has four specific goals. The first goal is to demonstrate an improved sol–gel process using rapid thermal annealing and a diluted sealant coating. The resulting thickness can reach 2 μm in three coatings with a crack-free area as large as 5 mm ×5 mm . The second goal is to characterize piezoelectric properties of the fabricated PZT films experimentally. The resulting piezoelectric constant d33 is 120 pC/N and the dielectric constant ranges from 200 to 400. The third goal is to demonstrate the use of the PZT thin film as a calibrated sensor. The specimen is a silicon cantilever ( 30 mm ×7.5 mm ×0.4 mm ) with a PZT thin film ( 4 mm ×4 mm ×1 μm ). Moreover, a tiny shaker excites the cantilever at the fixed end, and a charge amplifier detects the charge accumulated in the PZT film. In the meantime, a laser vibrometer measures the deflection of the cantilever at three points along the PZT film, from which the strain is calculated using Euler–Bernoulli beam theory. Comparison of the strain and the charge amplifier voltage determines the calibration constant of the PZT thin-film sensor. The last goal is to demonstrate the use of the PZT thin film as a powerful actuator through active vibration control. In experiments, a tiny bulk PZT patch is first glued to the silicon cantilever. A function generator drives the bulk PZT simulating a source of disturbance exciting the silicon cantilever. In the meantime, a laser Doppler vibrometer (LDV) measures velocity of the cantilever tip. With a phase shifter as the controller, the LDV measurement is fed back to the PZT thin-film actuator to actively control the cantilever vibration. To evaluate the effectiveness of the active vibration control, a spectrum analyzer measures the frequency response functions (FRF) from the bulk PZT voltage to the LDV response. Experimental results show that the simple active vibration control scheme can reduce resonance amplitude of the first bending mode by 66%.

Uniaxial compressive stress dependence of the high-field dielectric and piezoelectric performance of soft PZT piezoceramics

Abstract: The influence of uniaxial prestress on dielectric and piezoelectric performance was studied for soft lead zirconate titanate piezoceramics High electric field induced polarization and longitudinal/transverse strain were measured at different compression preload levels of up to −400 MPa The parameters evaluated included polarization/strain outputs, dielectric permittivity, piezoelectric constants, and dissipation energy as a function of the mechanical preload and electric-field strength The results indicate a significant enhancement of the dielectric and piezoelectric performance within a certain prestress loading range At much higher stress levels, the predominant mechanical depolarization effect makes the material exhibit hardly any piezoeffect However, the enhanced performance achieved by a small stress preload is accompanied by an unfavorable increased hysteresis, and consequently, increased energy loss, which is attributed to a larger extrinsic contribution due to more non-180° domain switching induced by the combined electromechanical load

Tip Deflection and Blocking Force of Soft PZT-Based Cantilever RAINBOW Actuators

Abstract: A piezoelectric/electrostrictive RAINBOW actuator is a monolithic bending device consisting of an electromechanically active layer and a reduced passive layer formed in a high-temperature reduction treatment. When the piezoelectric or electrostrictive layer is driven under an electric field or when the environmental temperature changes, bending deflection is produced because of the constraint of the reduced inactive layer or because of the thermal expansion coefficient difference of the two layers. In this study, general analytical expressions relating tip deflection, blocking force, and equivalent moment with an applied electric field and temperature change are derived for a cantilevered RAINBOW actuator. It is shown that optimal actuator performance can be achieved in the RAINBOW actuator by choosing a suitable thickness ratio of the reduced layer to the PZT layer. A series of RAINBOW cantilever actuators have been experimentally prepared from high-density, soft, lead zirconate titanate (PZT) ceramics. Different reduction layer thickness is obtained by adjusting the processing parameters, such as reduction temperature and time. The measured results on tip deflection and blocking force agree well with theoretical prediction under a weak electric field. However, when a high driving electric field is used, deviation is observed, which can be attributed to a nonlinear piezoelectric response and a nonlinear elastic behavior associated with soft PZT materials under high driving electric fields.

Pressure tuning of the morphotropic phase boundary in piezoelectric lead zirconate titanate

Abstract: Titanium-rich $\mathrm{PZT}$ solid solutions were studied under high pressure by neutron and x-ray diffraction, Raman spectroscopy and dielectric measurements. The results show that high pressure stabilizes the ferroelectric monoclinic phases, which are proposed to be responsible for the high piezoelectric properties characteristic of the morphotropic composition ${\mathrm{PbZr}}_{0.52}{\mathrm{Ti}}_{0.48}{\mathrm{O}}_{3}$. Pressure may thus be used to tune the morphotropic phase boundary in the composition-pressure plane to include a wide range of titanium-rich $\mathrm{PZT}$ compositions.