Showing papers on "Piezoelectricity 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...

Simple model for piezoelectric ceramic/polymer 1-3 composites used in ultrasonic transducer applications

Abstract: A theoretical model is presented for combining parameters of 1-3 ultrasonic composite materials in order to predict ultrasonic characteristics such as velocity, acoustic impedance, electromechanical coupling factor, and piezoelectric coefficients. Hence, the model allows the estimation of resonance frequencies of 1-3 composite transducers. This model has been extended to cover more material parameters, and they are compared to experimental results up to PZT volume fraction nu of 0.8. The model covers calculation of piezoelectric charge constants d/sub 33/ and d/sub 31/. Values are found to be in good agreement with experimental results obtained for PZT 7A/Araldite D 1-3 composites. The acoustic velocity, acoustic impedance, and electromechanical coupling factor are predicted and found to be close to the values determined experimentally. >

Piezoelectricity and pyroelectricity in polymers

Abstract: Piezoelectric properties of polymeric substances arise from either the poling-induced orientation of molecular dipoles (class 1) or the uniaxial orientation of chiral chain molecules (class 2). The class 1 polymers include ferroelectric polymers, polar polymers with frozen-in dipole orientation, and the composites of polymers with ferroelectric ceramics. Details of the poling procedure in representative materials are described, and optimum poling conditions are suggested. Resulting piezoelectric and pyroelectric activities are specified as a function of remnant polarization, and underlying basic mechanisms are summarized. The class 2 polymers consist of drawn optically active polymers and exhibit face-shear piezoelectricity appearing in proportion to the orientation coefficient of chain axes. The spontaneous polarization of ferroelectric liquid-crystalline polymers is attributable to this type of piezoelectricity coupled with the spontaneous strain. >

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...

Piezoelectric ceramics and ultrasonic transducers

Abstract: The author reviews the basic characteristics and progress in transducer properties of the different types of piezoelectric ceramics. The application of these materials in practical ultrasonic transducers is also reported.

Integrated scanning tunneling microscope

Abstract: There is disclosed herein an integrated scanning tunneling microscope and an integrated piezoelectric transducer and methods for making both. The device consists of one or two arm piezoelectric bimorph cantilevers (42, 46) formed by micromachining using standard integrated circuit processing steps. These cantilevers are attached to the substrate (32) at one area (80) and are free to move under the influence of piezoelectric forces which are caused by the application of appropriate voltages generated by control circuitry (88) and applied to pairs of electrodes (48, 36, 44; 52, 49, 44) formed as an integral part of the bimorph cantilever structure. The electric fields caused by the control voltages cause the piezoelectric bimorphs to move in any desired fashion within ranges determined by the design. The bimorph cantilevers have tips (66) with very sharp points formed thereon which are moved by the action of the control circuit (88) and the piezoelectric bimorphs so to stay within a very small distance of a conducting surface (84). The movements of the tip can be tracked to yield an image of the surface at atomic resolution.

Piezoelectric polymers

Abstract: Polymers with piezoelectric and pyroelectric properties that make them useful for biomedical applications and devices are considered. The characteristics of such polymers are examined, and transducers made from them are discussed. Laboratory developments of devices using piezoelectric polymers are briefly reviewed, and the slowness of product development in this area is commented on. >

Piezoelectric properties of III-V semiconductors from first-principles linear-response theory.

Abstract: We present a novel ab initio approach to piezoelectricity. The piezoelectric tensor is given by the stress induced by a homogeneous electric field. The perturbation is treated self-consistently by linear response, thus avoiding both supercells and numerical differentiation. We calculate the piezoelectric constants of none III-V semiconductors: as a by-product we also provide the first systematic study of zone-center phonons, internal strain parameters, effective charges, and dielectric constants. Our results agree very well with experiments where available, and allow predictions where they are not.

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...

Ferroelectric Properties of Tungsten Bronze Morphotropic Phase Bounary Systems

Abstract: Tungsten bronze ferroelectrics which have a morphotropic phase boundary (MPB) can have a number of enhanced dielectric, piezoelectric, and electrooptic properties compared to more conventional ferroelectric materials. The structural and ferroelectric properties of several MPB bronze systems are presented, including data from sintered and hot-pressed ceramics, epitaxial thin films, and bulk single crystals. Included among these are three systems which had not been previously identified as morphotropic. The potential advantages and limitations of these MPB systems are discussed, along with considerations of the appropriate growth methods for their possible utilization in optical, piezoelectric, or pyroelectric device applications.

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...

Large Piezoelectric Effect Induced by Direct Current Bias in PMN:PT Relaxor Ferroelectric Ceramics

Abstract: The longitudinal piezoelectric effect induced by a direct current bias field was investigated in PMN:PT family of relaxor ferroelectric ceramics in the frequency range from 0. 1 Hz to 50 kHz. The piezoelectric d33 coefficient was studied by measuring the strain induced by the applied electric field. Under the 10 kHz driving field, the large piezoelectric strain coefficient, d33, of 800 pC/N is obtained. The piezoelectric strain coefficient related dielectric and electrostrictive parameters were also studied under direct current bias and the d33 coefficient was calculated by the equation d33=2Q11P3e33. The results are in good agreement with the directly measured ones. The dispersion of the piezoelectric effect is mainly due to the dielectric dispersion.

The use of piezoelectric film and ultrasound resonance to determine the complete elastic tensor in one measurement.

Abstract: The ultrasonic and elastic properties of materials are conventionally measured using quartz, lithium niobate, etc., transducers and a pulse‐echo technique with the transducer driven at resonance. Problems with the technique include transducer ringing, transducer‐sample coupling, parallelism of sample faces, beam diffraction, and the necessity of remounting transducers in order to measure all of the elastic constants. Usually, these problems can be minimized, but with samples that are only a fraction of a millimeter in size, conventional ultrasound measurements become difficult if not impossible. However, nearly all of these problems may be avoided if a resonance technique is used, and all of the elastic constants may be determined with a single measurement. For the broadband response and minimum transducer loading required for a resonance measurement in a small sample, polyvinylidene flouride (PVDF) piezoelectric film (as thin as 9 μm) is ideally suitable.

High-frequency strain response in ferroelectrics and its measurement using a modified Mach-Zehnder interferometer

Abstract: In this paper we report on a modified Mach‐Zehnder interferometer which is capable of measuring the ultrashort time strain response of a sample Using this instrument, the dispersion of piezoelectric and electrostrictive coefficients of several commonly used ferroelectrics was measured The strain switching behavior of lead lanthanum zirconate titanate (PLZT) 9/65/35 driven by a square pulse electric field was studied The results show that the switching rise time of the strain response for PLZT 9/65/35 can be much shorter than 5 μs at a pulse field strength near 25 kV/cm and that the fall time of the strain response is considerably shorter than the rise time in the experimental field strength range

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.

Electromechanical coupling to Lamb and shear-horizontal modes in piezoelectric plates

Abstract: Recent theoretical studies and experiments have been shown that interdigital transducers can couple strongly to plate modes in piezoelectric materials and in piezoelectric-on-nonpiezoelectric composite membranes. The calculated velocity dispersion and electromechanical coupling factors for plate modes in representative piezoelectric materials are described. The frequency dependence of velocity and electromechanical coupling factors are given, under different metallization conditions, for generalized stiffened-Lamb, pure stiffened-Lamb, and stiffened-shear (shear-horizontal) modes, for various plate orientations in lithium niobate, lithium tantalate, quartz, bismuth germanium oxide, and zinc oxide. For lithium niobate, electromechanical-coupling values as high as 15% are found under narrowband bandpass conditions, and 5% under wideband low-pass conditions. For lithium tantalate, bismuth germanium oxide, coupling values of 0.5, 2, and 4% are obtained. For quartz with its weaker piezoelectricity, the coupling is still made smaller. >

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.

Piezoelectric properties and elastic constants of 4H and 6H SiC at temperatures 4–320 K

Abstract: 4H and 6H silicon carbide (SiC) crystals are piezoelectric and can be excited to resonant vibrations with quality factors up to Q≊100 000 and an electromechanical coupling factor of k31≊0.03 for 6H material. The resonance frequencies are used for the determination of elastic constants from 4 to 320 K. One finds a Poisson’s ratio σ=0.212 and low‐temperature values s11=2.035×10−12 m2/N and c33=55.12×1010 N/m2 for 6H, s11=2.114×10−12 m2/N, and c33=60.52×1010 N/m2 for 4H crystals. All elastic constants show a nonmonotonic dependence from the temperature at about 50 K.

Hysteresis-free piezoelectric actuators using LiNbO3 plates with a ferroelectric inversion layer

Abstract: Heat treatment of a bare single-domain lithium niobate plate at somewhat lower temperatures than the Curie temperature causes a local polarization reversal, thereby yielding a ferroelectric inversion layer. The plate with such an inversion layer can serve as a piezoelectric actuator similar to the bimorph, because the piezoelectric constants in the inversion layer are opposite in sign to the original ones. This paper reports the characteristics of the bending actuators using 140° rotated Y-cut LiNbO3. Experimental results show that the actuator characteristics have excellent linearity, no hysteresis, and little creep, and therefore they are suitable for precise position control.

Fiber-optic sensing of voltages by line integration of the electric field

Abstract: A fiber-optic sensor that is sensitive to the line integral of the electric field is presented. The sensor detects electric-potential differences by adding the scalar products of the local electric fields along the integration path times the path-segment vectors. This is achieved by exploiting symmetry properties of the converse piezoelectric effect. The sensor principle is experimentally demonstrated. Important performance parameters including integration accuracy, dynamic range, linearity, and bandwidth are examined.

Piezoelectric composite transducer for use in ultrasonic probe

Abstract: There is herein disclosed a piezoelectric composite transducer comprising a plurality of piezoelectric ceramic poles (1). The plurality of piezoelectric ceramic poles (1) are arranged two-dimensionally so as to form spaces (3) therebetween. Organic films (2) are disposed on both end surfaces of the plurality of piezoelectric ceramic poles (11) so that the spaces forms hollow portions (3). The hollow portions (3) causes making small its acoustic impedance up to a value close to the acoustic impedance of water or a human body.

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.

Measurement of all the elastic and dielectric constants of poled PVDF films

Abstract: As opposed to conventional piezoceramics, PVDF is a piezoelectric material, in polymer form. However, its properties are not well characterized due to the availability of poled PVDF only as a thin film. In the design of piezoelectric devices, properties such as all the components of the elastic stiffness tensor, dielectric tensor, and the electromechanical coupling tensor are needed. Poled PVDF is of mm2 symmetry. The frequency dependences of all nine complex elastic constants as well as the three complex dielectric constants were measured using a thin film and stacked, cubical samples of PVDF film. The elastic constants C/sup D//sub 44/ and C/sup D//sub 55/ as well as the dielectric constant epsilon /sup T//sub 11/ and epsilon /sup T//sub 22/ reported are new. Ultrasonic measurements and an impedance analyzer were used to obtain the measured data. >