Showing papers on "Lead zirconate titanate published in 1989"

Thermodynamic theory of the lead zirconate-titanate solid solution system, part I: Phenomenology

Abstract: Compositions within the lead zirconate-titanate (PZT) solid solution system have been extensively used in polycrystalline ceramic form in a wide range of piezoelectric transducer applications. However, the growth of good quality PZT single crystals for compositions across the entire phase diagram has not been accomplished. Due to the lack of single-crystal data, an understanding of the properties of polycrystalline PZT has been limited. If the single domain (intrinsic) properties of PZT could be determined, then the extrinsic contributions (e.g. domain wall and defect motions) to the polycrystalline properties could be separated from the intrinsic contributions. The purpose of this research has been to develop a thermodynamic phenomenological theory to model the phase transitions and single-domain properties of the PZT system. This paper is the first of a series of five papers describing the thermodynamic theory of PZT that has been developed for the entire solid solution system. In this paper th...

Thermodynamic theory of the lead zirconate-titanate solid solution system, part III: Curie constant and sixth-order polarization interaction dielectric stiffness coefficients

Abstract: Vaiues of the Curie constant (C) and sixth-order polarization interaction dielectric stiffness coefficients (α112 and α123) are needed for the development of a thermodynamic theory for the entire lead zirconate-titanate (PZT) solid solution system. Low-temperature dielectric data measured on pure homogeneous polycrystalline PZT samples were used to determine values of these coefficients at several compositions across the phase diagram. Equations were then fitted to these data to determine the compositional dependence of the coefficients. The Curie constant was found to form a peak in the middle of the phase diagram at the PZT 50/50 composition.

Field‐Forced Antiferroelectric‐to‐Ferroelectric Switching in Modified Lead Zirconate Titanate Stannate Ceramics

Abstract: Electric-field-forced antiferroelectric-to-ferroelectric phase transitions in several compositions of modified lead zirconate titanate stannate antiferroelectric ceramics are studied for ultra-high-field-induced strain actuator applications. A maximum field-induced longitudinal strain of 0.85% and volume expansion of 0.95% are observed in the ceramic composition Pb0.97La0.02(Zr0.66Ti0.09Sn0.25)O3 at room temperature. Switching from the antiferroelectric form to the ferroelectric form is controlled by the nucleation of the ferroelectric phase from the antiferroelectric phase. A switching time of <1 μs is observed under the applied field above 30 kV/cm. The polarization and strains associated with the field-forced phase transition decrease with increasing switching cycle, a so-called fatigue effect. Two types of fatigue effects are observed in these ceramic compositions. In one, the fatigue effects only proceed to a limited extent and the properties may be restored by annealing above the Curie temperature, while in the other, the fatigue effects proceed to a large extent and the properties cannot be restored completely by heat treatment. Hydrostatic pressure increases the transition field and the switching time. But when the applied electric field is larger than the transition field, the induced polarization and strain are not sensitive to increasing hydrostatic pressure until the transition field approaches the applied field.

Thermodynamic theory of the lead zirconate-titanate solid solution system, part V: Theoretical calculations

Abstract: In this final paper of a sequence of five papers presenting details of a thermodynamic phenomenology for the whole PbZrO3 : PbTiO3 solid solution family, the constants derived in the earlier papers are used to calculate the temperature and composition dependence of the Elastic Gibbs Free Energy ΔG 1 at zero stress, the spontaneous electric polarization and spontaneous tilt of the oxygen octahedra in a single domain, the anisotropic weak field dielectric permittivity and the piezoelectric constants for compositions all across the phase diagram. These data can be used to determine the intrinsic component of the behavior of any pure lead zirconate : lead titanate in any part of the phase field and at any temperature, and thus can form a first step in the separation of the experimentally observed properties into their intrinsic (single domain) component and their extrinsic domain and defect related responses. The function proposed is certainly not the final word for PZT, and will clearly be subjected...

Radiation effects on ferroelectric thin‐film memories: Retention failure mechanisms

Abstract: Ferroelectric thin‐film (200–350 nm) memories were fabricated and tested. Two materials were used as memory cells: potassium nitrate (KNO3) and lead zirconate titanate (PbZr0.54Ti0.46O3, usually abbreviated as PZT). These devices were tested as arrays deposited either by thermal evaporation (in the case of KNO3) or sputtered films (PZT). Fully packaged devices were tested to determine switching speed and polarization (switched charge) as functions of temperature and applied voltage. Radiation hardness was also tested for both dose rate and total dose. The switching kinetics were investigated in considerable detail and found to confirm the theory of Ishibashi. The dimensionality of domain growth for the switching process in KNO3 lowers from 2.3 before irradiation to 1.6 after 0.5 Mrad. For PZT rad hardness exceeds 5 Mrad total dose and 2×1011 rad/s. A surprising result was that the hysteresis curves for all of the PZT samples became more symmetric after 5 Mrad irradiation; this is interpreted as a destruct...

Process for making sol-gel deposited ferroelectric thin films insensitive to their substrates

Abstract: A method for producing a thin film of a ferroelectric perovskite material having the steps of providing a first substrate; depositing a first layer of a sol-gel perovskite precursor material wherein the crystallization of this precursor material to the pervoskite phase is insensitive to the first substrate; depositing a second layer of a sol-gel perovskite precursor material wherein the crystallization is sensitive to the first substrate; and heat-treating the deposited layers to form ferroelectric perovskites. A heat treatment step to form perovskites may optionally follow the deposition of the first layer. The first layer of sol-gel perovskite precursor material is selected to produce a perovskite upon heat treatment of: lead titanate (PbTiO3), or strontium titanate (SrTiO3). The second layer of sol-gel perovskite precursor material is selected to produce a perovskite upon heat treatment of: lead zirconate titanate (Pb(Zr,Ti)O3), lead zirconate (PbZrO3), lead lanthanum titanate ((Pb,La)TiO3), lead lanthanum zirconate ((Pb,La)ZrO3), lead lanthanum zirconate titanate ((Pb,La)(Zr,Ti)O3), lead magnesium niobate (Pb(Mg1/3 Nb2/3)O3), lead zinc niobate (Pb(Zn1/3 Nb2/3)O3), barium titanate (BaTiO3), strontium barium titanate ((Sr,Ba)TiO3), barium titanate zirconate (Ba(Ti,Zr)O3), potassium niobate (KNbO3), potassium tantalate (KTaO3), or potassium tantalate niobate (K(Ta,Nb)O3).

Low-Temperature Sintering of Lead-Based Piezoelectric Ceramics

Abstract: The low-temperature sintering of lead-based piezoelectric ceramics has been studied. The sintering temperature of lead zirconate titanate (PZT) ceramics could be reduced from ∼ 1250° to ∼960°C by the addition of a small amount of the lower-melting frit, B2O3–Bi2O3—CdO. It exhibited the following dielectric and piezoelectric properties: Kp= 0.52 to 0.58, Qm= 1000, eT33/e0= 800 to 1000, tan δ= 50 × 10−4, ρ= 7.56 to 7.64 g/cm3. Ceramics with the aid of suitable dopants (CdO, SiO2, and excess PbO) in the Pb-(Ni1/3Nb2/3)O3—PZT family could be sintered at 860° to 900°C. For these materials, Kp= 0.56 to 0.61, Qm= 1000, eT33/e0= 1500 to 2000, tan δ≤ 50 × 10−4, ρ= 7.80 to 8.03 g/cm3. The microstructure, sintering mechanism, and the effects of various impure additions have been analyzed by means of scanning electron microscopy, scanning transmission electron microscopy, electron probe microanalysis, and X-ray photoelectron spectroscopy.

Thermodynamic theory of the lead zirconate-titanate solid solution system, part II: Tricritical behavior

Abstract: Two tricritical points, where a phase transition changes from first to second order, were found to occur in the lead zirconate-titanate (PZT) solid solution system. High-temperature x-ray diffraction data on sol-gel derived PZT powders were used to calculate the cell parameters and spontaneous strain in the ferroelectric phases. These data were used with addition data from the literature to determine values of the higher-order dielectric stiffness coefficients, which were then used to locate the tricritical points. The values of the coefficients are also needed in the development of a thermodynamic theory of the PZT system.

Thermodynamic theory of the lead zirconate-titanate solid solution system

Abstract: Compositions within the lead zirconate-titanate (PZT) solid solution system have been extensively used in polycrystalline ceramic form in a wide range of piezoelectric transducer application. However, the growth of good quality PZT single crystals for compositions across the entire phase diagram has not been accomplished. Due to the lack of single crystal data, an understanding of the properties of ceramic PZT has been limited. If the single domain (intrinsic) properties of PZT could be determined, then the extrinsic contributions (e.g., domain wall and defect motions) to the ceramic properties could be separated from the intrinsic contributions. The purpose of this research has been to develop a thermodynamic phenomenological theory to model the phase transitions and single domain properties of the PZT system. A two-sublattice theory, where each sublattice has a separate polarization, was used to account for the ferroelectric and antiferroelectric phases. An additional order parameter was also i...

Thermodynamic theory of the lead zirconate-titanate solid solution system, part IV: Tilting of the oxygen octahedra

Abstract: Values of coefficients related to the tilting of the oxygen octahedra in the low-temperature rhombohedral phase of the lead zirconate-titanate (PZT) solid solution system are needed in the development of a thermodynamic theory of the PZT system. In this paper these coefficients will be determined from experimental spontaneous strain and oxygen octahedral tilt angle data. Values of the tilt angle related coefficients β1,β11, and φ are assumed to be independent of temperature, and are then related to P L, θL, and T R, where P L and θL are the spontaneous polarization and tilt angle of the low-temperature rhombohedral phase at the transition temperature T R between tilted and untilted structures. P L and θL are derived from experimental data for the PZT 90/10 composition, and used together with spontaneous strain values at this composition to determine electrostrictive (Q 44) and rotostrictive (R 44) constants. These constants are then in turn used to derive P L and θL values for other PZT compositi...

Piezoelectric ceramic compositional development

Abstract: The original piezoelectric ceramic material was unmodified barium titanate. It was little used except as compositionally modified. The earliest work was by W. P. Mason and this led to improved characteristics for sonar transducers and then to phonograph cartridge applications. By the mid 1950s, lead zirconate titanate (PZT) materials were shown by B. Jaffe to have higher piezoelectric coupling and application at much higher temperatures. Over the next 10 years, many modified compositions were developed. These led to much improved sonar systems and ultrasonic cleaners and to applications in ultrasonic bonders, stereo phonograph cartridges, and even printers. The new compositions also made possible applications such as piezoelectric ceramic filters, gas ignition devices, and camera flashbulb actuators. More recently, specialized ceramics have been developed based on lead titanate and lead metaniobate, but major efforts have been directed to applications of lead titanate zirconate compositions, which now tou...

Process for producing sub-micron ceramic powders of perovskite compounds with controlled stoichiometry and particle size

Abstract: A single crystal, solid solution, chemically homogenous powder that comprises a perovskite compound having useful electrical properties and the general formula: ABO₃, wherein the perovskite compound is selected from the group consisting of lead zirconate titanate, lead lanthanum zirconate titanate, lead titanate, lead zirconate, barium titanate, lead magnesium niobate, or lead zinc niobate, and having 0-50 percent total dopant or solid solution substitutions; and a process for making it.

Longitudinal Electrooptic Effects and Photosensitivities of Lead Zirconate Titanate Thin Films

Abstract: The feasibility of storing and reading high-density optical information in lead zirconate titanate (PZT) and in lead lanthanum zirconate titanate (PLZT) thin films depends on both the longitudinal electrooptic coefficients and the photosensitivities of the films. This paper describes the methods used to measure the longitudinal electrooptic effects and the photosensitivities of the films. The results of these measurements were used to evaluate a longitudinal quadratic electrooptic R coefficient, a longitudinal linear electrooptic rc coefficient, and the wavelength dependence of the photosensitivity of a composition of PZT polycrystalline thin film. The longitudinal electrooptic R and rc coefficients are about an order of magnitude less than the transverse R and rc coefficients of bulk ceramics of similar compositions. This is attributed to clamping of the film by the rigid substrate. The large birefringence of the films after poling (>10−2) suggests that the optic axes of the films are preferentially oriented normal to the film surface. The techniques used in this paper for evaluating the photosensitivities of thin films are based on measuring the photocurrent generated rather than the reduction in coercive voltage (as in bulk ceramics) when the film is exposed to light. The thin film photosensitivities appear to be significantly higher than those of bulk ceramics of similar compositions. The high photosensitivities coupled with the substantial longitudinal electrooptic coefficients combine to establish the feasibility of using PZT or PLZT thin films for optical information storage applications.

Composition and temperature dependence of the dielectric, piezoelectric and elastic properties of pure PZT ceramics

Abstract: Pure (undoped) piezoelectric lead zirconate titanate (PZT) ceramic samples at compositions across the ferroelectric region of the phase diagram were prepared from sol-gel-derived fine powders. Excess lead oxide was included in the PZT powders to obtain dense (95-96% of theoretical density) ceramics with large grain size (>7 mu m) and to control the lead stoichiometry. The dielectric, piezoelectric, and elastic properties were measured from 4.2 to 300 K. At very low temperatures, the extrinsic domain wall and thermal defect motions freeze out. The low-temperature dielectric data can be used to determine coefficients in a phenomenological theory. The extrinsic contribution to the properties can then be separated from the single-domain properties derived from the theory. >

Poling of Lead Zirconate Titanate Ceramics and Flexible Piezoelectric Composites by the Corona Discharge Technique

Abstract: In the conventional poling method, piezoelectric ceramics and composites are poled by applying a large dc voltage. Poling of composites having a polymer matrix with 0–3 connectivity is especially difficult because the electric field within the high-dielectricconstant grains is far smaller than in the low-dielectric-constant polymer matrix. Therefore, very large electric fields are required to pole these types of composites. However, large electric fields often cause dielectric breakdown of the samples. In this study for improved poling, the corona discharge technique was used to pole piezoelectric ceramics, fired PZT composites, and 0.5PbTiO3· 0.5BiFeO3 0–3 polymer composites. An experimental setup for corona poling is described. The dielectric and piezoelectric properties of materials poled by the corona discharge technique were comparable to those obtained with the conventional poling method.

Electrostrictive Properties of the lead Zirconate Titanate Solid-Solution System

Abstract: Values of the electrostrictive constants for the lead zirconate titanate (PZT) solid-solution system were required to com plete the development of a thermodynamic phenomenological theory of PZT. The electrostrictive Q12 constant was meas ured as a function of composition on polycrystalline ceramic PZT samples. These data were used with additional single–crystal and ceramic data from the literature to approximate the compositional dependence of the electrostrictive constants of the PZT system. Series and parallel equations, analogous to the Voigt and Reuss models for the elastic constants, were used to relate the ceramic and single-crystal data, and to pre dict the upper and lower bounds of the ceramic electrostric tive constants from the single-crystal constants.

Modified-lead-titanate/polymer composites for hydrophone applications

Abstract: Composite piezoelectrics made from Calcium-modified lead titanate rods embedded in a polymer matrix have been evaluated for hydrophone applications. These composites behave quite differently from the conventional 1–3 composites made with lead zirconate titanate ceramics. Specifically, in the modified lead-titanate case the magnitude of the d 31 coefficient is enhanced in the composite structure, and consequently the hydrostatic dh coefficient is suppressed. Nevertheless, these composites exhibit a large gh coefficient and a remark able pressure stability. An analysis shows that a substantial contribution to the composite's d 31 coefficient arises from internal stresses which develop along the ceramic rods and produce a piezoelectric charge through the d 33 coefficient of the ceramic. This effect is particularly pronounced in the composite structure of the modified lead-titanate ceramic since the ratio d 33/d 31 in this ceramic is exceptionally large.

Ferroelectric-Domain Structure in Piezoelectric Ceramics

Abstract: Twin-related (tetragonal (T), rhombohedral (R)) adjacent ferroelectric domains, which require a smaller energy for the rotation of the polarization vector, have been found to occur in lead zirconate titanate type piezoceramics at the morphotropicphase boundary, explaining the triplet splitting observed in electron diffraction patterns. The values of elastically stored energy density in the walls of the twinning domains are estimated, and a packing model of the ferroelectric domain structure as a T1RT2RT1…succession is proposed to explain the coexistence of the two ferroelectric phases in the morphotropicphase boundary region. A crystallographic analysis of the transformation from the paraelectric to the ferroelectric phase is performed on the basis of martensite transformation theory. The calculated results are in good agreement with the observed transmission electron microscopy data. In particular, the crystallography and morphology of the “herringbone” domain structure, often observed in piezoelectrio ceramics, are well explained by this analysis.

Mode coupling in modified lead titanate/polymer 1–3 composites

Abstract: Modified lead titanate/polymer 1–3 composites are fabricated and their resonance characteristics determined. The mode coupling theory is applied to the pillar‐shaped ceramic elements inside the 1–3 composite. Coupling of lateral and thickness mode vibrations occurs as the width to thickness ratio increases. The experimental results agree well with the mode coupling theory predictions. It is found that the piezoelectric properties of PbTiO3/epoxy composites are similar to that of lead zirconate titanate (PZT)/epoxy composites, except that the coupling constants of lead titanate are very small due to ceramic anisotropy. The thickness mode resonant frequency times the thickness value, fH, stays steady and close to the uncoupled value as the configurational (width/thickness) L/H ratio is increased from 0.1 to 1.0. In the range L/H=1.0–1.5, the thickness and lateral mode vibrations couple. Above L/H=1.5, these modes decouple and are easily resolved. The thickness mode becomes again close to the uncoupled value...

The influence of internal voids with 3–1 connectivity on the properties of piezoelectric ceramics prepared by a new planar process

Abstract: Using resonance measurements, the material properties of lead zirconate titanate samples with evenly spaced (anisotropic) internal voids were investigated. Ceramic/air-composites with 3–1 connectivity (0–15% voids) were produced using a new multilayer method. Essential to this new technique is a combination of photolithography with a stacking and pressing step of thin ceramic sheets. The results prove that the permittivity e, the mechanical quality factor Q t , the frequency constant in thickness direction N t , and therefore also the acoustical impedance Z of the investigated composites decrease greatly with increasing ratio of voids to bulk. The piezoelectric coupling k 32 perpendicular to the internal voids also decreases strongly. The coupling factors parallel to the voids k 31 and in thickness direction kt do not change from those of bulk material. The measurements are compared with calculations which were done using a simple model.

Influence of Microstructure on the Dielectric and Piezoelectric Properties of Lead Zirconate‐Polymer Composites

Abstract: Composites with 0–3 connectivity were fabricated from lead zirconate titanate (PZT) and phenolic resin powders. These composites were investigated for dielectric and piezoelectric properties with variations in active particle density and PZT-polymer interface porosity. The dependence of dielectric and piezolectric properties on interface porosity is discussed, especially in terms of porosity factors. The dependence of the piezoelectric constant on interface porosity was greater than that of the dielectric constant. The interface pores play the role of a stress buffer. Thus local stress applied on PZT particles in the composites was remarkably diminished. When particle porosity was high, the dependence of the dielectric and piezoelectric constants on interface porosity decreased.

Field‐Forced Antiferroelectric‐to‐Ferroelectric Switching in Modified Lead Zirconate Titanate Stannate Ceramics.

Abstract: Electric-field-forced antiferroelectric-to-ferroelectric phase transitions in several compositions of modified lead zirconate titanate stannate antiferroelectric ceramics are studied for ultra-high-field-induced strain actuator applications. A maximum field-induced longitudinal strain of 0.85% and volume expansion of 0.95% are observed in the ceramic composition Pb0.97La0.02(Zr0.66Ti0.09Sn0.25)O3 at room temperature. Switching from the antiferroelectric form to the ferroelectric form is controlled by the nucleation of the ferroelectric phase from the antiferroelectric phase. A switching time of <1 μs is observed under the applied field above 30 kV/cm. The polarization and strains associated with the field-forced phase transition decrease with increasing switching cycle, a so-called fatigue effect. Two types of fatigue effects are observed in these ceramic compositions. In one, the fatigue effects only proceed to a limited extent and the properties may be restored by annealing above the Curie temperature, while in the other, the fatigue effects proceed to a large extent and the properties cannot be restored completely by heat treatment. Hydrostatic pressure increases the transition field and the switching time. But when the applied electric field is larger than the transition field, the induced polarization and strain are not sensitive to increasing hydrostatic pressure until the transition field approaches the applied field.

Piezoelectric lead zirconate titanate coatings on metallic wires

Abstract: Acoustic measurements of thin piezoelectric lead zirconate titanate (PZT) films coated on metallic wires are presented. These experiments have demonstrated that PZT coatings fabricated by a sol-gel process can be not only coated on curved metal substrates for high-frequency focused ultrasonic transducer applications, but also on metallic wires with a long coating length for low-frequency acoustic vibrators.

Electrical and reliability characteristics of lead-zirconate-titanate (PZT) ferroelectric thin films for DRAM applications

Abstract: The electrical and reliability characteristics of lead-zirconate-titanate (PZT) ferroelectric capacitors are presented Thin Pb(Zr/sub 05/Ti/sub 05/)O/sub 3/ films of 350 nm were prepared using a solution-gelatin technique Hysteresis loop and pulse measurement methods indicate that PZT films exhibit a large charge storage density of 73 mu C/cm/sup 2/ and an equivalent dielectric constant of approximately 577 In addition, good endurance behavior (no fatigue or aging wearout after >10/sup 13/ cycles under accelerated unipolar stressing), reasonable transient characteristics (with estimated write time of approximately 01 ns and refresh time of approximately 25 s), and high effective breakdown field suggest that the PZT ferroelectric material has good potential for applications in advanced DRAMs (dynamic RAMs) >

Ultrasonic experiments with lead zirconate titanate thin films fabricated by sol gel processing

Abstract: Surface and bulk acoustic wave measurements with lead zirconate titanate (PZT) thin films fabricated by a sol gel processing technique are reported for the first time. The piezoelectricity of such films was achieved by poling. Good acoustic properties of these films are confirmed by the acoustic images and V(z) curves obtained by a scanning acoustic microscope.

Microstructure and electrical properties of fast-fired lead zirconate-titanate ceramics

Abstract: Fabrication de ceramiques PZT haute densite par frittage rapide (40 a 50 o C par nm). Etablissement de correlations entre les proprietes electriques et dielectriques et la densite et la grosseur de grain

Acoustic lenses employing PZT thin film transducers

Abstract: Acoustic lenses made of thin piezoelectric lead zirconate titanate (PZT) films fabricated by a chemical sol-gel process are presented. A frequency range between 50 and 250 MHz has been achieved. PZT films have been successfully coated on substrates such as fused quartz and metals, flat and cylindrical surfaces, and substrates with a large coating area or length. The piezoelectricity of the film is achieved by electric poling. The comparison between PZT and ZnO films for ultrasonic high frequency transducers is outlined.

Adhesion of electrolessly deposited nickel on lead zirconate titanate ceramic

Abstract: This paper reports on electrolessly deposited Ni onto lead zirconate titanate (PZT) ceramic measured as a function of both the ceramics surface preparation prior to metalization and the plated Ni thickness. A maximum in Ni/PZT interfacial adhesion of approximately 27 kg/cm{sup 2}, as measured by a pull test, occurs when the ceramic grain boundaries are chemically etched, thereby providing points to mechanically anchor the Ni deposit. The adhesion decreases with over-etching as the ceramic grains are undercut and drops off dramatically with increasing plated Ni thickness.

Microwave absorbers using ferroelectric/rubber composite structure and their evaluation

Abstract: A thin film microwave absorber is proposed using a ferroelectric/rubber composite (FRC) structure. The FRC structure consists of a lead zirconate titanate ferroelectric ceramic powder and a rubber composite. The operational principle and experimental results are discussed. A microwave absorber was obtained experimentally with a 1.65 mm thickness, yielding a bandwidth of 480 MHz at a central frequency of 8.6 MHz and analyzed theoretically.