Showing papers on "Ferroelectric ceramics published in 1995"
TL;DR: In this article, lead lanthanum zirconate titanate (PLZT) was loaded with compressive stress parallel to the polarization and the stress vs strain curve was recorded.
Abstract: Ferroelectric and ferroelastic switching cause ferroelectric ceramics to depolarize and deform when subjected to excessive electric field or stress. Switching is the source of the classic butterfly shaped strain vs electric field curves and the corresponding electric displacement vs electric field loops [1]. It is also the source of a stress—strain curve with linear elastic behavior at low stress, non-linear switching strain at intermediate stress, and linear elastic behavior at high stress [2, 3]. In this work, ceramic lead lanthanum zirconate titanate (PLZT) is polarized by loading with a strong electric field. The resulting strain and polarization hysteresis loops are recorded. The polarized sample is then loaded with compressive stress parallel to the polarization and the stress vs strain curve is recorded. The experimental results are modeled with a computer simulation of the ceramic microstructure. The polarization and strain for an individual grain are predicted from the imposed electric field and stress through a Preisach hysteresis model. The response of the bulk ceramic to applied loads is predicted by averaging the response of individual grains that are considered to be statistically random in orientation. The observed strain and electric displacement hysteresis loops and the nonlinear stress—strain curve for the polycrystalline ceramic are reproduced by the simulation.
651 citations
Journal Article•
TL;DR: In this article, the authors compare the properties of fine and coarse grained ceramics and compare them with relaxor and thin-firm Ceramics in terms of dielectric and elastic properties.
Abstract: Conventional ferroelectric perovskite type ceramics have dielectric, piezoelectric and elastic properties which depend on grain size and on domain configuration. Very fine grained ceramic is not splitted in domains. This causes strong elastic stress fields in the grains which counteract ferroelectricity. Tetragonal fine grained ceramic has a simple laminar domain structure and high elastic stress fields inside the grain and at the grain boundaries. These stress fields cause very high permittivity. In coarse grained ceramics the stress fields inside the grain are eliminated by a three-dimensional network of domains. In fine and in coarse grained ceramics the domain walls contribute considerably to the dielectric, piezoelectric and elastic constants at frequencies below a relaxation frecuency which is between 200 and 1000 MHz. At low temperatures, however, the domain wall contributions freeze in. Acceptor doping lowers the domain wall contributions and shifts the relaxation frequency to higher values. The properties of the conventional ceramics will be compared wiht properties of thin firms and with properties of relaxor ceramics.
269 citations
TL;DR: In this article, stable growth of cracks with either conducting or insulating interiors is observed in 8/65/35 lanthanum lead zirconate titanate samples.
Abstract: Ferroelectric ceramics are susceptible to fracture under high magnitude cyclic electric field. Flaws concentrate the electric field, inducing a large incompatible strain, and thereby a large stress. Stable growth of cracks with either conducting or insulating interiors is observed in 8/65/35 lanthanum lead zirconate titanate samples. Indentations on the electroded surface are filled with distilled water or a water-salt solution. Under cyclic electric field, tree like damage grows from the indented electrode. Indentations on the surfaces 90° to the electrodes are filled with silicone oil. This results in stable crack growth perpendicular to the cyclic electric field. Nonlinear fracture models are presented for both conducting and insulating cracks. Tensile stress intensity factors are predicted for both cases.
177 citations
TL;DR: In this article, the effects of heat treatment on phase and microstructure development for solution-and gel-derived ceramics are reported, and the efficiency with which carbonaceous species were eliminated during calcination of powders derived from sols or gels was investigated by thermal analysis, infrared spectroscopy, and helium gas pycnometry.
Abstract: We report the sol-gel processing of barium titanate (BaTiO{sub 3}) ceramics from methoxyethoxide precursors. The effects of heat treatment on phase and microstructure development for solution- and gel-derived ceramics are reported. Drying of monolithic alcogels yielded the low-temperature (T < 125 {degrees}C) crystallization of BaTiO{sub 3}. Crystallization was associated with gel syneresis. Nanocrystalline BaTiO{sub 3} gels which crystallized before the removal of solvent were used as monolithic precursors for the powderless processing of fine-grain dielectrics. Lower levels of hydrolysis content for solution-derived ceramics led to higher crystallization temperatures for the perovskite phase. In these cases, BaTiO{sub 3} crystallized via an intermediary oxycarbonate phase. The efficiency with which carbonaceous species were eliminated during calcination of powders derived from sols or gels was investigated by thermal analysis, infrared spectroscopy, and helium gas pycnometry. Dielectric properties were determined for dense ceramics derived form monolithic xerogels. Micrographs illustrate the development of structure for ceramics derived form the xerogel precursors. 27 refs., 9 figs.
125 citations
TL;DR: In this article, a lead lanthanum zirconate-titanate (LZT) ceramic was used to investigate the cyclic nature of cracks in a cyclic electric field of high magnitude.
Abstract: Ferroelectric ceramics are susceptible to stable crack growth under cyclic electric field of high magnitude. The stresses originate from mismatch strains induced by the electric field around inhomogeneities, such as processing flaws, terminated electrodes and the cracks themselves. The phenomenon is studied using a lead lanthanum zirconate-titanate ceramic. A flaw is indented on the surface of a ceramic sample. Subject to a cyclic electric field of magnitude exceeding the coercive field, cracks eminate from the flaw, in the direction perpendicular to the voltage drop. Tests relevant to the phenomenon are also performed. Polarization and strain as functions of applied electric field are measured at various temperatures and applied stresses. Discharge is demonstrated through an air gap between two ceramic plates subjected to a voltage drop. Models are presented that explain the cyclic nature of the crack growth.
81 citations
TL;DR: In this paper, a Michelson-Morley interferometer was used to study the frequency and temperature dependence of the complex piezoelectric and electrostriction coefficients of ferroelectric materials.
Abstract: In this paper, we report the development of a simple but precise piezoelectric spectrometer using a Michelson–Morley interferometer. The measurement system has been developed to study the frequency and temperature dependence of the complex piezoelectric and electrostriction coefficients of ferroelectric materials. The spectral data are collected by computer and has significantly wider frequency range and lower noise than other such systems. Results are reported for a quartz sample, a La‐modified lead zirconate titanate ferroelectric, and a lead zirconate titanate sol‐gel derived ferroelectric thin film.
70 citations
TL;DR: The voltage dependence of the dielectric constants in the paraelectric phase was examined in this article, where it was found that the voltage dependence was increased with the operating temperature above the Curie point.
Abstract: Ba1−xSrxTiO3x = 0.9) ferroelectric ceramics were prepared successfully using a new wet technique and their structure and dielectric properties compared with those synthesized by the solid-state reaction method. The voltage dependence of the dielectric constant in the paraelectric phase was examined. It was found that the dielectric constants of these materials, prepared by both methods, exhibit large changes with applied voltage in the paraelectric phase. Tunability (the percentage change of the dielectric constant from its zero-bias value in the presence of a de-biasing electric field) was observed to exceed 30% at only 1.7 kV/cm at 77 K in the samples prepared by the solid-state reaction method. The tunability was found to decrease dramatically as the operating temperatures increased above the Curie point. These observations are interpreted in light of an existing phenomenological theory. The dependence of the dielectric constant in the paraelectric state upon a de-biasing electric field is also demonstrated as a potential method for the characterization of dielectric nonuniformities in ferroelectric ceramics.
45 citations
TL;DR: In this article, a wide range of compositions possessing relaxor phase characteristics was found to exist near the boundaries between the ferroelectric rhombohedral, tetragonal and paraelectric cubic phases.
Abstract: Dielectric, ferroelectric and electric field-induced strain properties of (Pb1-xBax)(Zr1-yTiy)O3 ceramics with 0.15 ≤ x ≤ 0.45 and 0.16 ≤ y ≥ 0.70 were investigated. A wide range of compositions possessing relaxor phase characteristics was found to exist near the boundaries between the ferroelectric rhombohedral, tetragonal and paraelectric cubic phases. Within this compositional range, broadened peaks of dielectric constant as a function of both composition and temperature were identified as well as slim loop hysteresis and frequency-dependent relaxation behavior. Longitudinal field-induced strain for some selected samples and transverse strain for all the compositions studied were determined. Maximum total and differential strains were found in the vicinity of the rhombohedral-tetragonal phase boundary. Optimal values of the differential strain were close to (about 80%) those found in PLZT ceramics. Inside the relaxor phase region the relationship between the strain and electric field (or polar...
37 citations
TL;DR: In this paper, the growth and properties of PbS thin films, chemically deposited on bulk lead titano-zirconate ceramics, are investigated using scanning electron microscopy photographs.
Abstract: The growth and properties of PbS thin films, chemically deposited on bulk lead titano‐zirconate ceramics, are investigated. Scanning electron microscopy photographs reveal that the medium size of crystallites is much larger for PbS films grown on poled ferroelectric substrates than for the films grown onto glass or onto unpoled ferroelectric substrates. In the first case the medium size of crystallites is about 1–1.5 μm while in the second case it is less than 0.3 μm. Spectral distribution of photoconductivity and thermally stimulated currents (TSC) measurements were performed on all samples. Experimental results indicate that the properties of the PbS films can vary, depending on the substrate nature and in the case of poled ferroelectric substrates, on the polarity. The photoconductive signal is usually larger, the dark resistivity is smaller, and the TSC current value is higher for PbS films deposited on the positive face of the ferroelectric substrate than for those deposited on the negative face.
31 citations
TL;DR: In acceptor doped perovskite type ceramics, the decrease of the complex dielectric constant and the build-up of electric and elastic internal bias fields are caused by the slow orientation of dipola as mentioned in this paper.
Abstract: In acceptor doped perovskite type ceramics the decrease of the complex dielectric constant and the build-up of electric and elastic internal bias fields are caused by the slow orientation of dipola...
29 citations
TL;DR: In this article, the asymptotic behavior of stress and electric fields near the intersections of domain walls with grain boundaries is analyzed and the analysis concludes that both the stress and the electric fields exhibit a power-law singularity, with r being the radial coordinate originating at the intersecting point and λ being a constant whose value is within the range (1 0).
Abstract: Experimental investigations suggest that microcracking may be the major cause for the commonly encountered degradation of ferroelectric actuators, namely electric fatigue. It is commonly believed that stress concentration is responsible for the onset of cracking although the quantitative relation between these two events has not been understood completely. It is expected that formation of ferroelectric twins, i.e., 90° domains, can cause severe stress concentration at intersections of domain walls with grain boundaries because of the incompatibility of lattice distortions with grain boundary constraints. This article presents an analysis upon the asymptotic behavior of stress and electric fields near these intersections. The asymptotic analysis is carried out within a framework of electrostatics for deformable continua. Assuming that the electromechanical state in each of the ferroelectric domains is slightly distorted from one of the natural states of the crystal, the authors developed a piecewise linearized model for which concentrations of stress and electric fields correspond to singularities of these fields. The analysis concludes that both the stress and the electric fields exhibit a power-law singularity; i.e., their magnitudes are proportional to rλ, with r being the radial coordinate originating at the intersecting point and λ being a constant whose value is within the range (–1,0). The examples included show that the severity of concentration depends upon the crystal orientation and the orientations of the domain walls with respect to the grain boundary which they intersect. Considering the microcracks may be generated during the cooling or poling process, the authors have also studied the interaction of ferroelectric twins with preexisting microcracks, both intergranular and transgranular. The analysis indicates that this interaction makes the singularity substantially stronger than the conventional √r-singularity and hence it suggests that this interaction promotes crack growth.
TL;DR: In this paper, a measurement system was designed and constructed which is capable of automatic data collection for complex piezoelectric d33 constant (amplitude and phase), field-induced polarization and switching current under high electric field driving in ferroelectric materials.
Abstract: A measurement system has been designed and constructed which is capable of automatic data collection for complex piezoelectric d33 constant (amplitude and phase), field-induced polarization and switching current under high electric field driving in ferroelectric materials. The system is based on the direct piezoelectric effect and d33 constant can be measured down to about 10 pC/N. Using this system, low and high electric field piezoelectric responses were examined in soft lead zirconate titanate (PZT) ceramics by comparing the data with the total polarization and strain changes. At a low a.c. electric field, the observed complex piezoelectric d33 constant measured by the direct piezoelectric method is equal to the values measured by the converse piezoelectric method, and the field-induced strain is fully accounted for the complex piezoelectric d33 constant. At a high electric field, however, the amount of total strain becomes larger than the estimated strain by integrating d33 in terms of electric field. The contribution of irreversible domain wall motion to the total strain change was found to approach 51.5% at the electric field strength of +1400 V/mm. The newly developed system can quantitatively determine the lattice motion and reversible domain wall motion-induced strain component in the total strain response under the high electric field driving in piezoelectric ceramics.
TL;DR: The dielectric step from the free condition to the clamped condition at the relaxation frequency is on the order of {Delta{var_epsilon} {approx} 10-100 as mentioned in this paper.
Abstract: Periodic domain configurations with alternating 180{degree} and 90{degree} domains are not completely mechanically clamped up to microwave frequencies. Above the acoustic resonance of the ferroelectric sample, therefore, the dielectric constant comprises contributions which can be attributed to the free dielectric constant. Up to microwave frequencies the domains are piezoelectrically active; they emit longitudinal and shear thickness waves into the surroundings which cause dielectric loss in the sample. The dielectric step from the free condition to the clamped condition at the relaxation frequency is on the order of {Delta}{var_epsilon} {approx} 10--100. This step is much smaller than the step caused by the emission of shear waves from 90{degree} domain walls.
TL;DR: In this paper, the effect of oxidation and reduction atmospheres on the ferroelectric behavior of bismuth titanate was investigated, and the effective surface density of free charges in samples polarized by applying an electric field E/sub p/=1 MV m/sup -1/ at a temperature of 100/spl deg/C for 90 min was determined by compensation voltage measurements.
Abstract: The effect of oxidation and reduction atmospheres on the ferroelectric behavior of bismuth titanate was investigated. The effective surface density /spl sigma//sub eff/ of free charges in samples polarized by applying an electric field E/sub p/=1 MV m/sup -1/ at a temperature of 100/spl deg/C for 90 min was determined by compensation voltage measurements. The thermally treated samples in oxidation atmospheres exhibit a significant decrease of /spl sigma//sub eff/ while those treated in a reducing atmosphere exhibit an increase accompanied by an improvement in the stability of the electret charge. Such observations indicate that the formation as well as the transformation of the electret state of Bi/sub 4/Ti/sub 3/O/sub 12/ ceramics may be related to the enhancement and diminishing of oxygen vacancies. In all cases homocharge with a time independent sign was obtained. >
TL;DR: In this paper, the compatibility of sol-gel processed Pb(Zr,Ti)O3 (PZT) thin films with thin film shape memory effect TiNi substrates was investigated.
Abstract: Thin film layers of shape memory alloys and ferroelectric ceramics can produce a family of ‘‘smart’’ heterostructures capable of performing both sensing and actuating functions. Important issues in the synthesis of these active structures are the ability to generate the appropriate crystalline phases of each material while producing defect‐free homogeneous high quality films. The compatibility of sol–gel processed Pb(Zr,Ti)O3 (PZT) thin films with thin film shape memory effect TiNi substrates were investigated. Thin film TiNi was deposited on quartz substrates by physical sputter deposition utilizing a TiNi target in a ultrahigh vacuum chamber, which was followed by in situ vacuum annealing. The ferroelectric tetragonal phase of PZT was deposited on TiNi by sol–gel and spin coating processes followed a by 600 °C anneal for 5 min in air. The heterostructures obtained were nominally defect‐free, unlike those obtained through deposition onto bulk TiNi substrates.
02 Feb 1995
TL;DR: In this paper, a series of experiments on lead lanthanum zirconate titanate are modeled with a computer simulation of the ceramic microstructure, and the polarization and strain for an individual grain are predicted from the imposed electric field and stress through a Preisach hysteresis model.
Abstract: Ferroelectric and ferroelastic switching cause ferroelectric ceramics to depolarize and deform when subjected to excessive electric field or stress. Switching is the source of the classic butterfly shaped strain vs. electric field hysteresis loops and the corresponding electric displacement vs. electric field loops. It is also the source of a stress-strain curve with linear elastic behavior at low stress, non-linear switching strain at intermediate stress, and linear elastic behavior at high stress. In this work, a series of experiments on lead lanthanum zirconate titanate are modeled with a computer simulation of the ceramic microstructure. The polarization and strain for an individual grain are predicted from the imposed electric field and stress through a Preisach hysteresis model. The response of the bulk ceramic to applied loads is predicted by averaging the response of individual grains that are considered to be statistically random in orientation. The random orientation yields essential non-linear behavior of the observed strain and electric displacement hysteresis loops and the non-linear stress- strain curve for the polycrystalline ceramic. The linear piezoelectric effect opens up a butterfly shape to the strain vs. electric field hysteresis loop but the model fails to predict the observed effect of 90 degree(s) switching. The grain to grain residual stress and residual polarization are estimated from inclusion calculations. These are both a function of the remanent strain and remanent polarization of the ceramic. This constraint opposed switching but has little effect on the butterfly shape in the strain vs. electric field hysteresis loop.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: In this paper, the ferroelectric properties of Pb(Fe1/2Ta 1/2)O3 ceramics, in particular on the electromechanical properties, were investigated.
Abstract: Investigations were conducted on the ferroelectric properties of Pb(Fe1/2Ta1/2)O3 ceramics, in particular, on the electromechanical properties. Dense ceramic specimens prepared by the hot-pressing technique were used in this study. At the temperature of 158 K, the following values were obtained: e T33/e0=1450, P r=10.8 µ C/cm2, k33=0.390 and d33=131×10-12 C/N. These values were briefly compared with those of Pb(Fe1/2Nb1/2)O3 ceramics.
TL;DR: In this paper, the Curie temperature and the maximum dielectric constants increase as the amount of additives increases in PMN-based ferroelectric ceramics, and unipolarly induced strains become smaller than bipolarly induced strain as the temperature decreases.
Abstract: The Curie temperature and the maximum dielectric constants increase as the amount of additives increases in PMN-based ferroelectric ceramics. The Tc of PMN, 0.9MN-0.1PT, and 0.8PMN-0.2PZT is ca. 0°C, 40°C and 65°C, respectively. Bipolar-induced strains rarely change with temperature in the ferroelectric phase below Tc. The plots of polarization vs. electric field are consistent with the S-E plots. The coercive field and remanent strain of PMN-based materials increase as the temperature decreases below Tc. Consequently, unipolarly induced strains become smaller than bipolarly induced strains as the temperature decreases. The temperature of maximum strain is lower than Tc by ca. 30°C in 0.8PMN-0.2PZT and 0.9PMN-0.1PT. The temperature of maximum strain is ca. 10°C and 30°C, in 0.9PMN-0.1PT (Tc=40°C) and 0.8PMN-0.2PZT (Tc=65°C), respectively, and is expected to be -30°C in PMN (Tc=0°C).
01 May 1995
TL;DR: In this article, experimental results obtained using Lead-Zirconate-Titanate (PZT) ceramic as the electron source in a planar diode geometry are presented and results from a theoretical model are compared to these measurements.
Abstract: In the past decade a number of research groups have studied electron emission from ferroelectric ceramics. These materials have saturation polarization P/sub s/, of up to 100 /spl mu/C/cm/sup 2/. The emission occurs when the polarization state of the ferroelectric is changed rapidly by an applied electric field, and a fraction of the surface screening charge is released. We report experimental results obtained using Lead-Zirconate-Titanate (PZT) ceramic as the electron source in a planar diode geometry. Experimental measurements of time-dependent variations in the emission are presented and results from a theoretical model are compared to these measurements. We also present new data on the scaling of the emission current density for anode voltages of up to 50 kV. The new data will be used in the design of an electron gun using a ferroelectric cathode.
05 May 1995
TL;DR: In this article, the authors investigated the interactions of ferroelectric twins with grain boundaries and pre-existing microcracks and showed that the stress fields exhibit a power-law singularity at the intersecting points of twinning planes and grain boundaries.
Abstract: Ferroelectric crystals are widely used for manufacturing smart actuators owing to their strong electromechanical coupling effect and the prompt response to the applied electric fields. Many ferroelectric actuators are operated under cyclic loading conditions. The cyclic-loading strengths of these materials are, however, substantially lower than their monotonic-loading strengths. It has been observed that the macroscopic properties of these materials deteriorate after a large number of cycles of the applied electric field. This is the so-called electric fatigue. Recent experimental investigations suggest that microcracking may be the major cause of electric fatigue. The authors investigated the interactions of ferroelectric twins with grain boundaries and pre-existing microcracks. They have demonstrated that the stress fields exhibit a power-law singularity at the intersecting points of twinning planes and grain boundaries. This concentration in stresses may initiate microcracks at the intersecting points. They have also shown that the formation of ferroelectric twins at a pre-existing crack tip results in stronger singularities of the stress and electric fields than the common (root)r-singularity. This indicates that the interaction between the ferroelectric twins and the microcracks may promote crack growth.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Patent•
09 Aug 1995
TL;DR: In this article, a novel ferroelectric ceramics have the formula xPMN-yPt-zPZN (I) in which either z is not zero or the compsn. process for forming a piezoelectric ceramic.
Abstract: of EP0666244Novel ferroelectric ceramics have the formula xPMN-yPt-zPZN (I) in which either z is not zero or the compsn. (x,y,z) is located at the boundary (morphotropic phase) between two ferroelectric phases of different symmetrics, one being of relaxor or diffuses transition type (for PMN) and the other being of tetragonal crystallographic structure (for PT). In (I), PMN = lead magno-niobate, Pb(Mg1/3NB2/3)O3; PT = lead titanate, PbTiO3; and PZN = lead zinco-niobate, Pb(Zn1/3Nb2/3)O3. Also claimed are (i) prodn. of the above ferroelectric ceramics; (ii) uses of the above ferroelectric ceramic, having a non-zero polarisation in one direction, as a piezoelectric ceramic, and (iii) use of the above prodn. process for forming a piezoelectric ceramic.
TL;DR: In this article, the model of sintering processes occurring in ferroceramic materials as percolation phase transition is suggested, and the results of a computer simulation of SIS based on percolations models are presented.
Abstract: The model of sintering processes occurring in ferroceramic materials as percolation phase transition are suggested. The results of a computer simulation of sintering processes based on percolation models are presented.
07 Nov 1995
TL;DR: In this paper, the authors developed highly accurate lumped equivalent networks for these frequencies, for the two canonical cases of thickness-and lateral-field excitation, which permit the extraction of the complex dielectric, piezoelectric and elastic parameters of the ceramic material.
Abstract: Future applications for ferroelectric ceramics include thin-film resonant microstructures for timing, sensing, and actuation. The frequency range of interest extends from nearly DC through the UHF band. At high frequencies especially, it is difficult to obtain precise material parameters from broadband electrical measurements. We have developed highly accurate lumped equivalent networks for these frequencies, for the two canonical cases of thickness- and lateral-field excitation. Measurements on these circuits permit the extraction of the complex dielectric, piezoelectric, and elastic parameters of the ceramic material. A numerical example is given.
02 Feb 1995
TL;DR: In this paper, a piecewise linearized model was developed for which concentrations of stress and electric fields correspond to singularities of these fields, and the analysis was carried out within a frame work of electrostatics for deformable continua.
Abstract: Experimental investigations suggest that microcracking may be the major cause for the commonly-encountered degradation of ferroelectric actuators, namely electric fatigue. The present analysis, based upon the lattice distortions occurring during the formation of electric twins, indicates that intersections of domain walls with grain boundaries are likely to be origins of microcracks because of the concentrations of stress and electric fields arising due to the incompatibility of the lattice distortions with the grain boundary constraints. This further motivated an asymptotic analysis on the stress and electric field concentrations near intersections of domain walls with grain boundaries. This analysis is carried out within a frame work of electrostatics for deformable continua. Assuming that the electromechanical state in each of the ferroelectric domains is slightly distorted from one of the natural states of the crystal, the authors developed a piecewise linearized model for which concentrations of stress and electric fields correspond to singularities of these fields. The asymptotic analysis concludes that both the stress and electric fields exhibit a power-law singularity. Several examples indicate that the order of singularity depends upon the crystal orientation and the orientations of the domain walls with respect to the grain boundary which they intersect.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
25 Jun 1995
TL;DR: In this article, the longitudinal piezoelectric effect in ferroelectric ceramics is investigated as a function of amplitude and frequency of external pressure, the crystal structure and microstructure of a given composition.
Abstract: The longitudinal piezoelectric effect in ferroelectric ceramics is investigated as a function of amplitude and frequency of external pressure, the crystal structure and microstructure of ceramics. The domain wall contribution to the piezoelectric response is the dominant extrinsic origin of the instability of the observed piezoelectric effect, but, for a given composition, can be affected by dopants and microstructure. Other sources of instabilities in piezoelectric response, such as chemical inhomogeneities and defects, are also discussed.
TL;DR: In this paper, a controllable lens for ultrasonic beam focussing in non-uniform electric fields of special configurations is presented, based on the quadratic electroacoustic effect.
TL;DR: An improved quantitative pyroelectric characterization system has been developed in an effort to more thoroughly investigate the dynamic pyro electric response of selected materials at particular temperatures of interest, such as at transition, or to study electrical aging effects as discussed by the authors.
Abstract: An improved quantitative pyroelectric characterization system has been developed in an effort to more thoroughly investigate the dynamic pyroelectric response of selected materials at particular temperatures of interest, such as at transition, or to study electrical aging effects. Specifically, the system is capable of measuring pyroelectric current responsivity of a wide variety of materials ranging from ferroelectric ceramics to polymers at constant temperature utilizing a modulated heating source technique.' Effectiveness of this system was determined through measurements of lithium tantalate and lithium niobate samples of various geometries. The result of the study was a comprehensive evaluation of dynamic pyroelectric current responsivity of these samples with a particularly good signal-to-noise enhancement for evaluating high noise materials such as polymer gels which are extremely difficult to evaluate using other techniques. These measurements revealed a significant dependence of the pyro...
01 Jan 1995
TL;DR: In this paper, the longitudinal piezoelectric effect in ferroelectric ceramics is investigated as a function of amplitude and frequency of external pressure, the crystal structure and microstructure of a given composition.
Abstract: SUMMARY The longitudinal piezoelectric effect in ferroelectric ceramics is investigated as a function of amplitude and frequency of external pressure, the crystal structure and microstructure of ceramics. The domain wall contribution to the piezoelectric response is the dominant extrinsic origin of the instability of the observed piezoelectric effect, but, for a given composition, can be affected by dopants and microstructure. Other sources of instabilities in piezoelectric response, such as chemical inhomogeneities and defects, are also discussed.
01 Jan 1995
TL;DR: In this paper, the sot-gel method for preparation of ferroelectric ceramics can offer many advantages over conventional processing techniques, such as high degrees of purity and homogeneity, can produce fme powders as well as being able to be formed into a variety of structures and they possess the ability to be processed at lower temperatures.
Abstract: : The nature of the pyroelectric properties of the composite %Ca/Epikote 828 with 50/50 and 60/40 vol% was reported in the fifth interim report. The present report provides an account of the preparation of pure lead titanate (H) and calcium modified lead titanate (%Ca) by the Sol-Oel process. X-ray Spectroscopic Structural Analysis and Differential Scanning Calorimetric (DSC) studies of the ceramic grains produced by this technique were made and the results are given in this report. The sot-gel method for preparation of ferroelectric ceramics can offer many advantages over conventional processing techniques. Ceramics produced via the sol-gel method show high degrees of purity and homogeneity, can produce fme powders as well as being able to be formed into a variety of structures and they possess the ability to be processed at lower temperatures.
22 May 1995
TL;DR: In this paper, the compatibility of sol-gel-processed Pb(Zr,Ti)O3 (PZT) thin films with thin film shape memory effect TiNi substrates was investigated.
Abstract: Thin film layers of shape memory alloys and ferroelectric ceramics can produce a family of smart heterostructures capable of performing both sensing and actuating functions. Important issues in the synthesis of these active structures are the ability to generate the appropriate crystalline phases of each material while producing defect-free homogeneous high-quality films. The compatibility of sol-gel-processed Pb(Zr,Ti)O3 (PZT) thin films with thin film shape memory effect TiNi substrates were investigated Thin film TiNi was deposited on quartz substrates by physical sputter deposition utilizing a TiNi target in a ultrahigh-vacuum chamber, which was followed by in- site vacuum annealing. The ferroelectric tetragonal phase of PZT was deposited on TiNi by sol-gel and spin-coating processes followed by a 600 degree(s)C anneal for 5 m in air. The heterostructures obtained were nominally defect-free, unlike those obtained through deposition onto bulk TiNi substrates.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.