Showing papers on "Piezoelectricity published in 1981"
TL;DR: A review of the physical properties of polyvinylidenefluoride (PVDF) with particular emphasis on its piezoelectric activity is given and the applications of this material are discussed as discussed by the authors.
Abstract: A review of the physical properties of polyvinylidenefluoride (PVDF) with particular emphasis on its piezoelectric activity is given and the applications of this material are discussed. PVDF is a semicrystalline polymer whose crystalline domains appear in four different forms. These forms may be interconverted by the application of heat, electrical fields, and pressure. Thermal poling or corona poling will orient the molecular dipoles in the crystalline parts and thus yield a permanent polarization. This polarization causes, by means of differences in the dielectric and elastic properties of the amorphous and crystalline parts, the piezoelectricity of PVDF. The piezoelectric constant d31 reaches values of about 35 pC/N at room temperature. At decreasing temperatures a drop of d31 and d33 is observed. Compared to other piezoelectric materials, PVDF has such unique properties as flexibility, ruggedness, availability as thin films, and low acoustic impedance, but a somewhat smaller electromechanical coupling factor. Applications of PVDF are in transducers for audiofrequency, ultrasonic, underwater, and electromechanical use and in pyroelectric and optical devices.
383 citations
TL;DR: In this paper, composites containing 10 to 70 volume percent PZT were prepared with several different rod diameters, and measured dielectric constants ranged from 200 to 1000, longitudinal piezoelectric coefficients d33 from 200- 350 pC/N, and hydrostatic PZE coefficients dh from 40 to 80 pC /N.
255 citations
TL;DR: In this article, the product of the electrostriction coefficientQ and the Curie-Weiss constantC is constant for all perovskite crystals and the Q value is proportional to the square of the thermal expansion coefficient,α.
Abstract: Properties of new electrostrictive materials for displacive transducers are reviewed including theoretical, material and design studies. Intensive investigation of the electrostrictive effects in ferroelectric and antiferroelectric perovskites have led to some empirical rules: the product of the electrostriction coefficientQ and the Curie-Weiss constantC is constant for all perovskite crystals and theQ value is proportional to the square of the thermal expansion coefficient,α. Consistent with the empirical rules, the relaxor ferroelectric ceramic 0.9 Pb(Mg1/3Nb2/3)O3 −0.1 PbTiO3 possesses much larger strain with lower hysteresis, aging effects and thermal expansion than that obtained with piezoelectric lead zirconate titanate (PZT). Using a multilayer configuration similar to commercial capacitors, a new mirror control device capable of large strains with high reproducibility, up toΔL/L ∼ 10−3, with only 200 V applied has been developed.
222 citations
01 Jan 1981
TL;DR: In this article, the elastic stiffness, piezoelectricity and permittivity of AlN were determined by computer calculation from the experimental results on SAW phase velocities and electromechanical coupling coefficients.
Abstract: We have determined the material constants of AlN,i.e., elastic stiffness, piezoelectricity and permittivity, by computer calculation from the experimental results on SAW phase velocities and electromechanical coupling coefficients. A1N films used were single-crystal films on the basal plane of sapphire grown by metalorganic chemical vapor deposition. Until now, very few of these material constants are known. We report, for the first time, all the matrix elements of the material constants. The calculated variations of SAW phase velocities and coupling constants with A1N film thickness on basal and R planes of sapphire were in good agreements with the reported experimental results. Next, using the evaluated material constants, it was shown that the highfrequency (UHF) and low-dispersion SAW characteristics (less than 0.1% velocity change for ~20% bandwidth) with a large coupling (4%) can be expected for AlN/Si and AlN/SOS, when the c-axis of A1N was aligned along the surface of (001) Si.
128 citations
Patent•
04 Jun 1981
TL;DR: In this article, a piezoelectric fluid-electric generator including a bending element, means for mounting one end of the bending element in a fluid stream, and electrode means connected to the bend element to conduct the current generated by the oscillatory motion of the bend.
Abstract: A piezoelectric fluid-electric generator including: a piezoelectric bending element; means for mounting one end of the bending element in a fluid stream; means for driving the piezoelectric bending element to oscillate with the energy of the fluid stream; and electrode means connected to the piezoelectric bending element to conduct current generated by the oscillatory motion of the piezoelectric bending element.
118 citations
TL;DR: The dielectric, elastic and electrostrictive constants of polyvinylidene fluoride (pvdf) are influenced by thermal molecular motion, particularly at the glass transition temperature.
104 citations
Patent•
05 Jan 1981
TL;DR: In this paper, a piezoelectric generator for converting acoustic energy in a predetermined frequency range to electric energy is described, including means for mounting the bending element in an acoustic energy path.
Abstract: A piezoelectric generator for converting acoustic energy in a predetermined frequency range to electric energy including: a piezoelectric bending element; means for mounting the piezoelectric bending element in an acoustic energy path; tuning means mounted to the piezoelectric bending element to set the resonant frequency of oscillation of the piezoelectric bending element within the predetermined frequency range.
97 citations
TL;DR: The results indicate that barium titanate ceramic shows a very high degree of biocompatibility as evidenced by the absence of inflammatory or foreign body reactions at the implant-tissue interface, making this material a new candidate for further tests for hard tissue replacement.
Abstract: The suitability of barium titanate (BaTiO3) ceramic for direct substitution of hard tissues was evaluated using both electrically stimulated (piezoelectric) and inactive (nonpolarized) test implants. Textured cylindrical specimens, half of them made piezoelectric by polarization in a high electric field, were implanted into the cortex of the midshaft region of the femora of dogs for various periods of time. Interfacial healing and bio-compatibility of the implant material were studied using mechanical, microradiographical, and histological techniques. Our results indicate that barium titanate ceramic shows a very high degree of biocompatibility as evidenced by the absence of inflammatory or foreign body reactions at the implant-tissue interface. Furthermore, the material and its surface porosity allowed a high degree of bone ingrowth as evidenced by microradiography and a high degree of interfacial tensile strength. No difference was found between the piezoelectric and the electrically neutral implant-tissue interfaces. Possible reasons for this are discussed. The excellent mechanical properties of barium titanate, its superior biocompatibility, and the ability of bone to form a strong mechanical interfacial bond with it, makes this material a new candidate for further tests for hard tissue replacement.
95 citations
TL;DR: In this article, a piezoelectric array is mounted on one or more tires of a motor vehicle, and the vehicle is flexed during each revolution to distort the piezelectric elements and generate electricity.
Abstract: A piezoelectric array is mounted on one or more tires of a motor vehicle. As the vehicle drives down the road, the tire is flexed during each revolution to distort the piezoelectric elements and generate electricity. An electric circuit delivers the energy to the electrical system of the vehicle.
92 citations
TL;DR: In this paper, a small central region of a thin sheet of the polymer polyvinylidene fluoride locally piezoelectric, and then supporting the sheet in the field by holding it taut in a metal hoop having dimensions larger than the field being probed, is presented.
Abstract: Miniature piezoelectric polymer hydrophones for ultrasonic field characterization in the low megahertz region have been developed and tested. The principal advantages of these devices over conventional hydrophones are their uniform frequency response and minimal perturbation of the field. These characteristics are achieved by rendering a small central region of a thin sheet of the polymer polyvinylidene fluoride locally piezoelectric, and then supporting the sheet in the field by holding it taut in a metal hoop having dimensions larger than the field being probed. Both single elements having diameters less than 1 mm and multielement arrays have been formed on the polymer. Methods of construction, signal amplification, and, in one design, rf shielding are discussed, and data are presented on insertion loss, sensitivity, frequency response, and immunity to rf interference.
84 citations
TL;DR: In this paper, the induced piezoelectric stress constant e 31 by poling was interpreted fairly well by the theory proposed by Wada and Hayakawa in terms of three factors; μ31, μ′c and K31.
Abstract: Electrostriction constant (K31) and Poisson's ratio of a film (μ31, μ21) and that of a crystal (μ′) were measured for uniaxially drawn and rolled poly(vinylidene fluoride) films. The highly stretched films showed the large values of MH (∼0.8). μc(∼ 4.0) and K31(∼ 30). These values depend strongly on the structures of films such as crystal structure and molecular orientation. The induced piezoelectric stress constant e 31 by poling was interpreted fairly well by the theory proposed by Wada and Hayakawa in terms of three factors; μ31, μ′c and K31. Contribution of each factor to the piezoelectricity was evaluated. Among them, the Poisson's ratio of a film has the largest effect which amounts to 50% of the total piezoelectric activity.
TL;DR: In this article, the authors used a charge amplifier to measure the three orthogonal polarizations of charge produced by an applied stress on a cubic sample of pure quartz and compared them with the expected statistical effect for a rock of that grain size and composition.
TL;DR: In this article, the authors defined the deflection-bandwidth product (DBWP) and showed that when energy transfer is nonessential, the DBWP is a useful figure of merit.
Abstract: Resonance and deflection behavior are discussed for a variety of electrically driven flexure-type devices. The deflection-bandwidth product (DBWP) is defined, and it is shown that when energy transfer is nonessential, the DBWP is a useful figure of merit. For piezoelectric and magnetostrictive devices, the maximum DBWP is a function of materials parameters only and not device dimensions. Even though the piezoelectric constants of poly(vinylidene fluoride) (PVF2) are much lower than those of typical ceramics, the maximum DBWP is higher. Theoretical and experimental results show that piezoelectric bender “bimorph” performance can be improved by using a relatively thick, low-density, low-modulus bonding layer.
Patent•
29 Jul 1981
TL;DR: In this paper, a dual pyroelectric crystal sensor for infrared intruder alarms is presented. But the sensor includes a single-ended field effect transistor amplifier with the entire sensor encapsulated in a TO-5 can.
Abstract: A dual pyroelectric crystal sensor suitable for infrared intruder alarms and the like having two separate closely spaced identical pyroelectric crystal detectors connected in parallel opposition. The sensor includes a single ended field effect transistor amplifier with the entire sensor encapsulated in a TO-5 can. The two crystals each have one end cemented to a ceramic substrate in a cantilevered fashion, permitting shock or vibration to affect each crystal equally. Therefore, voltages due to the piezoelectric responses of the crystals are equal and cancel. If both crystals are irradiated by a common heat source, the pyroelectric generated voltages will cancel. If either crystal is irradiated separately, an output voltage will be produced.
TL;DR: In this paper, a new technique for constructing both linear and matrix array transducers using completely separated piezoelectric elements whose vibration modes have been studied experimentally is described.
TL;DR: In this paper, a description of intrinsic stress in thin films deposited on anisotropic (piezoelectric) substrates is obtained from the rotationally invariant equations of nonlinear elasticity (and electroelasticity).
Abstract: A description of intrinsic stress in thin films deposited on anisotropic (piezoelectric) substrates is obtained from the rotationally invariant equations of nonlinear elasticity (and electroelasticity). The accompanying residual stress state in the substrate is, of course, included in the description, as is the residual stress state in the thin film. The equations for small dynamic fields superposed on the static (intrinsic plus residual) bias are obtained, and the equation for the perturbation in eigenfrequency of a piezoelectric resonator due to the intrinsic and residual stress state is presented. The static biasing equations for both extension and flexure of the plated crystal plate, which are required for the determination of the residual stress state from the intrinsic stress state, are obtained. The important case of a thin film deposited on one side of a plate substrate is treated in detail, and the relation of the flexural curvatures of the plated plate to the components of the intrinsic stress i...
Patent•
13 May 1981
TL;DR: In this article, a transducer element in the form of a thermoformed protuberance is presented for detecting and generating elastic compression waves, for infrared radiation, and for storing electrical energy.
Abstract: The invention relates to devices using transducer elements comprising a film of piezoelectric polymer arranged between electrodes. The transducer element in accordance with the present invention is in the form of a thermoformed protuberance. These devices are used for detecting and generating elastic compression waves, for infrared radiation, and for storing electrical energy.
TL;DR: In this paper, a general review of the connection between piezoelectricity and crystal symmetry is presented, noting that a recent arrival on the scene (ferroelasticity) is intimately related to crystal symmetry rules.
Abstract: The two basic physical phenomena involved in all piezoelectric devices are wave propagation and resonance. A general review is first presented of the connection between piezoelectricity and crystal symmetry, noting that a recent arrival on the scene (ferroelasticity) is intimately related to crystal symmetry rules for piezoelectricity and promises to be applicable to new devices in the future. Special features peculiar to wave propagation in piezoelectric materials are noted and a brief sketch is given of methods used for solving piezoelectric boundary value problems.
[...]
TL;DR: In this paper, high pyroelectric responses were observed in these glass-ceramics and values of piezoelectric d33 coefficients, frequency constants, electromechanical coupling coefficients and dielectric properties were in close agreement with the values of respective single crystals.
Abstract: Pyroelectric-piezoelecric glass ceramics of polar materials like Li2Si2O5, Ba2TiGe2O8, Ba2TiSi2O8, and Various compositions in the systems Li2O-B2O3, Li2O-SiO2-ZnO, Li2O-SiO2-B2O3 have been prepared by oriented recrystallization of the glasses under a strong temperature gradient, providing a simple inexpensive process for preparing piezoelectric and pyroelectric materials. High pyroelectric responses were observed in these glass-ceramics. Values of piezoelectric d33 coefficients, frequency constants, electromechanical coupling coefficients and dielectric properties of glass-cermics were in close agreement with the values of respective single crystals.
TL;DR: In this paper, a theory of electron mobility for a two-dimensional electron gas scattered by piezoelectric phonons is developed, and the mobility values are then computed for different compound semiconductors at different lattice temperatures.
Abstract: A theory of electron mobility for a two-dimensional electron gas scattered by piezoelectric phonons is developed. The mobility values are then computed for different compound semiconductors at different lattice temperatures. It is found that piezoelectric-scattering-limited mobilities in GaAs, InSb and InAs are smaller than acoustic-phonon-scattering-limited mobility while in strong piezoelectric materials like CdS and ZnO, piezoelectric scattering is more dominant.
TL;DR: In this study, a dry long bone has been modeled as a piezoelectric, transversely isotropic hollow cylinder, and an analytic solution for this electro-mechanical wave propagation in a long bone for the flexural vibration.
TL;DR: Ferroelectric SBN single crystals have been successfully grown in this article, where Piezoelectric, high frequency dielectric and surface acoustic wave properties have been examined and reported.
Abstract: Ferroelectric SBN single crystals Sr61Ba39Nb2O6 approximately one inch in diameter have successfully been grown Piezoelectric, high frequency dielectric and surface acoustic wave properties of the SBN crystals have been examined and are reported
TL;DR: In this article, the authors obtained the triboluminescence spectra of organic molecular crystals belonging to the triclinic crystal system and showed that when the crystals are subjected to rapid mechanical strain, their triboluminous activity first increases as a function of the square of the time and then decays exponentially with the square root of time.
TL;DR: In this paper, results from a variety of experiments carried out by the authors on the photoacoustic spectroscopy of solids and surfaces by employing an indigenous spectrometer are discussed in the light of the recent literature.
Abstract: After briefly reviewing the theory and instrumentation, results from a variety of experiments carried out by the authors on the photoacoustic spectroscopy of solids and surfaces by employing an indigenous spectrometer are discussed in the light of the recent literature. Some of the important findings discussed are, phase angle spectroscopy, anomalous behaviour of monolayers, unusual frequency dependence in small cell volumes, spectra of a variety of solids including amorphous arsenic chalcogenides, photoacoustic detection of phase transitions and determination of surface areas and surface acidities of oxides. Recent developments such as piezoelectric photoacoustic spectroscopy, depth profiling and subsurface imaging are also presented.
TL;DR: In this paper, it was shown that knowledge of the sound speeds of a virgin and a poled specimen of a ferroelectric ceramic and certain associated properties of the hysteresis and butterfly loops permits the characterization of its equilibrium material properties in the polar direction consistent with an explicit version of the constitutive relations for the stress and the electric displacement.
Abstract: The mechanical, piezoelectric and dielectric properties of ferroelectric ceramics can be quite complicated. These materials exhibit both instantaneous and transient responses depending on various physical mechanisms such as dipole dynamics and domain switching. Hence the constitutive relations for the stress and the electric displacement which have been formulated are quite complicated and their characterization can be rather intricate. These constitutive relations must also describe the equilibrium responses of the ceramics when the transient processes have come to rest. In the paper, we show that knowledge of the sound speeds of a virgin and a poled specimen of a ferroelectric ceramic and certain associated properties of the hysteresis and butterfly loops permits the characterization of its equilibrium material properties in the polar direction consistent with an explicit version of the constitutive relations for the stress and the electric displacement.
Patent•
13 Nov 1981
TL;DR: In this paper, electric domain reversals are arranged in parallel arrays on a piezoelectric ceramic substrate to form strong reflectors of surface acoustic waves in devices such as filters, resonators and the like.
Abstract: Electric domain reversals are arranged in parallel arrays on a piezoelectric ceramic substrate to form strong reflectors of surface acoustic waves in devices such as filters, resonators and the like. The domains are prepared by a poling process involving the use of a selective electrode pattern to which a high DC voltage is applied at a temperature above ambient but below the Curie temperature of the substrate.
TL;DR: Using ferroelectric hysteresis, the remanent polarization, P r, was measured at room temperature as a function of frequency and maximum electric field in this article, where the electric field was applied with a triangular wave form in the frequency range 3 × 10−3 to 4 × 102 Hz.
Abstract: Using ferroelectric hysteresis, the remanent polarization, P r, was measured at room temperature as a function of frequency and maximum electric field. The electric field was applied with a triangular wave form in the frequency range 3 × 10−3 to 4 × 102 Hz and in a maximum field range of 100 kv/cm to 2.5 Mv/cm. As a result of this data, estimates of the switching time for polarization reversal are given as a function of the applied electric field. These switching times were also measured using conventional time-domain techniques and compared with those values obtained from the frequency dependence of the remanent polarization. Measurements of the piezoelectric stress coefficient, g 31, were then made on samples with known remanent polarizations. The resulting linear correlation coefficients were compared with those obtained from a molecular dipole model.
Patent•
13 Aug 1981
TL;DR: In this paper, the authors proposed a method to facilitate impedance matching with an external circuit by forming two partial electrodes opposing to a floating partial electrode through a piezoelectric thin film in between, and then leading electric terminals out of those partial electrodes.
Abstract: PURPOSE:To facilitate impedance matching with an external circuit by forming two partial electrodes opposing to a floating partial electrode through a piezoelectric thin film in between, and then leading electric terminals out of those partial electrodes. CONSTITUTION:On a subtrate 21 of silicone, crystal, etc., having a hole 22 by etching, a thin film 23 of a semiconductor such as silicon oxide, silicon nitride, and silicon doped with boron or an insulator is formed, and then a piezoelectric thin film 24 of zinc oxide, aluminum nitride, etc., is formed thereupon. On the thin film 23, a floating electrode 25 is formed and the partial electrodes 26 and 27 are provided on the piezoelectric thin film 23 opposing to the floating electrode 25. Then when electric terminals are led out of the partial electrodes 26 and 27 and energized electrically, oscillation is performed in such a way that when the overlap between the electrodes 26 and 25 extends in the thickness direction, the overlap between the electrodes 27 and 25 contracts in the thickness direction.
TL;DR: In this article, the long term stability of biaxially-oriented poly(vinylidene fluoride) has been examined in isothermal aging from a few minutes to a few months, log e vs. time shifts between 6O°C at 88°C are characterized to have an activation energy of 1.2 eV.
Abstract: The long term stability of biaxially-oriented poly(vinylidene fluoride) has been examined. In isothermal aging from a few minutes to a Few months, log e vs. time shifts between 6O°C at 88°C are characterized to have an activation energy of 1.2 eV. Data on uniaxial poled commercial film shows agreement with this result. Long term room temperature stability of pyroelectricity over a 10 year span augmented other elevated temperature data in supporting the conclusion that thermally activated processes should not be a factor in device reliability.