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Showing papers on "Piezoelectricity published in 1975"


Journal ArticleDOI
TL;DR: In this article, the piezoelectricity of PVDF thermoelect rets formed with vacuum-coated aluminum electrodes has been investigated in detail, and it was shown that the β-form crystal structure of the PVDF homopolymer and copolymers is not attributed to the stress dependence of spontaneous polarization, but rather to the persistent polarization arising from trapped charges.
Abstract: The piezoelectricity of PVDF thermoelect rets formed with vacuum-coated aluminum electrodes has been investigated in detail. The piezoelectricity depends on the β-form crystal structure of PVDF homopolymer and copolymers. However, the piezoelectricity is not attributed to the stress dependence of the spontaneous polarization of β-form crystals, but rather to the persistent polarization arising from trapped charges. The trapping mechanism is discussed.

76 citations


Journal ArticleDOI
TL;DR: It is confirmed that the electrical signals produced by samples of dried bone and tendon bent in the cantilever mode are d.c. square waves in response to step loading.

75 citations


Journal ArticleDOI
TL;DR: The piezoelectric stress coefficient and electrostriction coefficient for unpoled and poled films of polyvinylidene fluoride have been determined by applying a sinusoidal electric field and detecting stresses with the same and double frequency as the applied field, respectively as mentioned in this paper.
Abstract: The piezoelectric stress coefficient and electrostriction coefficient for unpoled and poled films of polyvinylidene fluoride have been determined by applying a sinusoidal electric field and detecting stresses with the same and double frequency as the applied field, respectively. The piezoelectric coefficient shows a hysteresis with the cyclic change of the d.c. bias field. Under the poling field, the dipoles in polymers are preferentially oriented in the direction of the field, thus producing a residual polarization associated with a residual stress. Both coefficients increase with increasing temperature. A phenomenological interpretation for the piezoelectricity in poled polymers is given in terms of electrostriction and residual stress.

74 citations


Journal ArticleDOI
20 Feb 1975-Nature
TL;DR: In this article, a simple longitudinal stress system with sinusoidally varying drive was used to measure both converse and direct piezoelectric coefficients of bone as functions of humidity and ultimately of moisture content.
Abstract: FUKADA and Yasuda1 showed that dry bone is piezoelectric in the classic sense, that is, mechanical stress produces polarisation (direct effect) and application of an electric field produces strain (converse effect)2. The possibility that the mechanism for osteogenesis is electrical3 has aroused interest in an investigation of such effects in the more nearly physiological condition represented by wet bone. Recent developments in electrical stimulation of fracture healing4,5 have further emphasised the importance of characterising the piezoelectric properties of wet bone. As the piezoelectricity of wet collagen6 decreases to zero at a moisture content equal to 45% of the dry weight (which corresponds to almost 100% humidity)7, there is some doubt as to whether wet bone could be piezoelectric. Observations of voltages in wet bone under stress, have been made under conditions giving such ambiguous results that they suggested alternative concepts to that of classic piezoelectricity8–11. In view of the confusion about the nature of the voltage developed when wet bone is stressed, we have used a simple longitudinal stress system with sinusoidally varying drive, to measure both converse and direct piezoelectric coefficients of bone as functions of humidity (and ultimately of moisture content). The results show unambiguously that wet bone behaves as a piezoelectric material.

64 citations


Patent
19 Dec 1975
TL;DR: By filling the container of a piezoelectric stack with a dielectric fluid under sufficient pressure, or applying sufficient pressure to a solid dieellectric, to maintain dieelessicle particle velocity and piezelessric particle velocity substantially spaced as mentioned in this paper, the failure of the piezelized stack is prevented.
Abstract: By filling the container of a piezoelectric stack with a dielectric fluid under sufficient pressure, or applying sufficient pressure to a solid dielectric, to maintain dielectric particle velocity and piezoelectric particle velocity substantially spaced, dielectric breakdown with consequent arc over and destruction of the piezoelectric stack is prevented.

59 citations


Patent
03 Jan 1975
TL;DR: In this paper, a temperature compensated surface acoustic wave device with an SiO 2 film layer upon a substrate of piezoelectric material is presented, where the positive temperature coefficient of delay of the substrate is counterbalanced by the negative temperature coefficients of the SiO2 layer.
Abstract: A temperature compensated surface acoustic wave device having an SiO 2 film layer upon a substrate of piezoelectric material. The positive temperature coefficient of delay of the piezoelectric substrate is counterbalanced by the negative temperature coefficient of the SiO 2 layer. The thickness and shape of the SiO 2 layer are chosen to give a zero first order temperature coefficient for the composite device. Lithium niobate and lithium tantalate are preferred piezoelectric materials for the substrate. A high degree of temperature stability is thereby obtained with coupling coefficients much greater than were previously obtained by prior temperature compensated surface acoustic wave devices.

45 citations


Journal ArticleDOI
TL;DR: In this paper, the elastic and piezoelectric constants of ferroelectric lead potassium niobate were measured by the use of the thickness vibrations of plates, and it was shown that the y-cut plate has the largest coupling factor of 0.73 for the shear mode and the z−cut plate had the smallest coupling factor (0.59) for the extensional mode.
Abstract: All the elastic and piezoelectric constants of ferroelectric lead potassium niobate were measured by the use of the thickness vibrations of plates. Calculating the electromechanical coupling factors of rotated cuts, it was shown that the y‐cut plate has the largest coupling factor of 0.73 for the shear mode and the z‐cut plate has the largest coupling factor of 0.59 for the extensional mode. If the piezoelectricity arises from the effect of each oxygen octahedron, the metal ions seem to displace parallel to one of the 4mm axes of the oxygen octahedron within the tetragonal c plane.

41 citations


Journal ArticleDOI
TL;DR: In this article, wave propagation and thickness vibrations in two-layered piezoelectric plates are investigated by the three-dimensional theory of piezelectricity and approximate theories.
Abstract: Wave propagation and thickness vibrations in two−layered piezoelectric plates are investigated by the three−dimensional theory of piezoelectricity and approximate theories. Piezoelectric materials of hexagonal symmetry are considered. The sixfold axes of the materials are assumed to be parallel or perpendicular to the plate. Dispersion curves and frequencies for thickness vibrations are presented. The electromechanical coupling effect is examined and

35 citations


Patent
08 Aug 1975
TL;DR: In this paper, a polymeric piezoelectric layer of material is connected at its ends to a support means in such a way that it can readily vibrate, and a weight is attached to the polymeric layer to act as an inertial mass to accentuate bending of such layer in response to movement of the support means.
Abstract: A piezoelectric polymer transducer for converting mechanical energy into electrical energy includes a transducing means formed of a polymeric piezoelectric layer of material that is connected at its ends to a support means in such fashion that it can readily vibrate. The piezoelectric layer is coated on at least an outer portion of each of its planar surfaces with conductive electrodes and a weight is attached to the piezoelectric layer to act as an inertial mass to accentuate bending of such layer in response to movement of the support means.

31 citations


Journal ArticleDOI
TL;DR: Interferometric measurements of bovine bone and tendon show that the values of the piezoelectric strain constant d14 decrease with hydration from the dry values, indicating that the electric dipoles in bone collagen are subject to a different cancelling mechanism.

28 citations



Journal ArticleDOI
TL;DR: In this paper, the authors used a reciprocity coupler to measure g33 and KT33 accurately as a function of one-dimensional stress to high values of stress, and found that the peaks are due to a phase transition from the ferroelectric tetragonal to the Ferroelectric rhombohedral state.
Abstract: Highly accurate data obtained from measurements on three different formulations of lead zirconate titanate piezoelectric ceramic material show the dependence of g33, d33, and KT33 on one‐dimensional stress (applied parallel to the direction of polarization) to high values of stress (0–400 MPa). The constants for one type of ceramic vary with stress less than those of the other two types for high values of stress. A peak in the curve of tanδ as a function of T3 for two types of materials is a function of the material, and it is believed that the peaks are due to a phase transition from the ferroelectric tetragonal to the ferroelectric rhombohedral state. The experimental feasibility and practicability of using a reciprocity coupler to measure g33 and KT33 accurately as a function of one‐dimensional stress to high values of stress has been established.

Patent
14 Jul 1975
TL;DR: An electro-acoustic transducer consisting of a flexible film of piezoelectric material, at least one electrode provided on one side of said film and a plurality of electrodes provided on the other side of the film to form a piezelectric diaphragm and imparted with a locally differing resiliency and/or tension, is provided.
Abstract: An electro-acoustic transducer comprising a flexible film of piezoelectric material, at least one electrode provided on one side of said film and a plurality of electrodes provided on the other side of said film to form a piezoelectric diaphragm and said piezoelectric diaphragm is imparted with a locally differing resiliency and/or tension, is provided. By using this piezoelectric electro-acoustic transducer in a loudspeaker, it is possible to improve acoustic characteristics thereof particularly in a high frequency range, to obtain a variety of acoustic characteristics and to effect motional feed back to minimize distortion of reproduced sound without involving any difficulty in manufacturing or affecting proper performance of the transducer.


Patent
21 Mar 1975
TL;DR: In this article, an electro-mechanical transducer in the form of interleaved comb shaped electrodes deposited on the substrate and covered by a piezoelectric layer was used to convert the received light energy into a modulation of an electric signal.
Abstract: A device which converts the spatial distribution of the received light energy into a modulation of an electric signal. It comprises: a non-piezoelectric substrate; an electro-mechanical transducer in the form of interleaved comb shaped electrodes deposited on the substrate and covered by a piezoelectric layer, and a photoconductive layer covering the piezoelectric layer. The image is projected on to the photoconductive layer and, when the transducer is short-circuited, an elastic wave modulated by the image is propagated in the substrate towards an output transducer which delivers the electric reading signal.

Journal ArticleDOI
TL;DR: Use of hydrophobic membrane filters is shown to effectively reduce the interfering moisture level in the detection of SO2 in air at the parts per billion range.
Abstract: Use of hydrophobic membrane filters is shown to effectively reduce the interfering moisture level in the detection of SO2 in air at the parts per billion range. Quadrol is used as a sensitive coating on piezoelectric crystal detectors in a flow system.

Patent
13 Jun 1975
TL;DR: In this article, a piezoelectric crystal film is formed by sputtering of source material which is in the form of a convex curved surface or a polyhedral surface and the formed film has crystallographic properties which can be very well controlled.
Abstract: A crystal film such as a piezoelectric crystal film is formed by sputtering of source material which is in the form of a convex curved surface or a polyhedral surface, and the formed film has crystallographic properties which can be very well controlled.


Journal ArticleDOI
TL;DR: In this paper, an apparatus was devised for measuring the real and imaginary components of the piezoelectric strain constant d = d′ − id″ for polymer films with a d.c. bias field.
Abstract: An apparatus is devised for measuring the real and imaginary components of the piezoelectric strain constant d = d′ − id″ for polymer films with a d.c. bias field. Electric fieldinduced piezoelectricity is observed for films of several types of polymer. The ratio of the piezoelectric constant to the d.c. bias field gives (ϵ + κ)/G where ϵ is the dielectric constant, κ is the electrostriction constant, and G is the elastic constant. The temperature dependence of the field-induced piezoelectricity gives, therefore, combined information of dielectric and elastic properties of polymers. After heating to about 95°C followed by cooling to room temperature, maintaining a constant d.c. basis on a poly(vinyl chloride) film, piezoelectricity is observed at null d.c. field, which suggests the introduction of a residual polarization in the films.

Journal ArticleDOI
TL;DR: In this article, the four piezoelectric moduli of InPS 4 have been determined, and they differ considerably in magnitude, one of them being about 10 times as large as the maximal modulus (d 11 ) of quartz.


Journal ArticleDOI
TL;DR: In this article, a theory governing the transducer properties of the piezoelectric insulator FET transducers is presented, which relates the drain current of the device to induced polarizations of the layer.
Abstract: An oriented piezoelectric film incorporated in the insulator region of a silicon insulated-gate field-effect transistor (FET) results in a sensitive high-frequency strain transducer. Theory governing the transducer properties of the piezoelectric insulator FET transducer is presented. Equations are developed which relate the drain current of the device to induced polarizations of the piezoelectric layer. The highest frequency of surface strains to which the FET transducer can respond is determined by the FET frequency response - ultimately by the channel transit time. This frequency can extend to the GHz range. The low-frequency response to applied strain is determined by the dielectric relaxation frequency of the piezoelectric layer.

Journal ArticleDOI
TL;DR: In this article, the dispersion relation has been derived and the distribution of the electric potential and the particle displacement as a function of the depth has been estimated numerically for the chosen media of ZnO and GaYIG.
Abstract: This paper presents some useful discussions on the surface wave guided by the interface of two semi‐infinite media in contact, of which one is piezoelectric and the other magnetoelastic The dispersion relation has been derived and the distribution of the electric potential and the particle displacement as a function of the depth has been estimated numerically for the chosen media of ZnO and GaYIG Subsequently, it has been shown that the nonreciprocal transmission characteristics in the narrow band can be obtained when two media have different elastic constants

Patent
12 Feb 1975
TL;DR: In this article, a piezoelectric electro-acoustic transducer employing as a diaphragm a uniaxially stretched film of a shape having the major axis and the minor axis, wherein the expansion-contraction direction of the diaphrasm, in which a piezelectric constant is at a maximum, is substantially in parallel with the minoraxis thereof, is described.
Abstract: A piezoelectric electro-acoustic transducer employing as a diaphragm a uniaxially stretched film of a shape having the major axis and the minor axis, wherein the expansion-contraction direction of the diaphragm, in which a piezoelectric constant is at a maximum, is substantially in parallel with the minor axis thereof, whereby the piezoelectric electro-acoustic transducer can provide a high converting efficiency, especially in the low frequency range.


Patent
28 Aug 1975
TL;DR: In this article, separate polarizing electrodes are attached to the opposite surfaces of a thermoplastic film to polarize the film to produce an electric element, such as an electret, piezoelectric or pyroelectric element.
Abstract: OF THE DISCLOSURE Separate polarizing electrodes are attached to the opposite surfaces of a thermoplastic film. A high D.C. voltage is then applied across these electrodes to polarize the film to produce an electric element, such as an electret, piezoelectric or pyroelectric element. Portions of the polarizing electrodes are then selectively removed to form the operating electrodes required for the electric element.

Patent
16 Dec 1975
TL;DR: In this article, a multi-layer metal molecular adhesion bond is used to connect a high frequency and wide-band ultrasonic component with a sound medium, which is then ground to a desired thickness in order to obtain a desired resonant frequency.
Abstract: An acousto-optical component or other high frequency and wide-band ultrasonic component comprises a piezoelectric transducer and a crystalline or glass sound medium which are bonded together by a multi-layer metal molecular adhesion bond. During fabrication, the surfaces of the piezoelectric body and the sound medium which are to be connected are first polished to a degree of smoothness which is well below that of a Newton ring. These surfaces are then completely cleansed and a first metal layer having a thickness of 0.5-2 nm is vapor deposited onto each the cleansed surfaces. Next, a second metal layer having a thickness of 5-20 nm is vapor deposited onto each of the first layers. The transducer is then applied, by molecular adhesion, to the sound medium. To form a strong and reliable bond, only moderate pressures of about 250 to 1500 psi are necessary. A metal layer having a thickness of 0.3-0.6 μm is vapor deposited over an extending portion of the multi-layer bond as a terminal for connection to a high frequency supply. Subsequently, the transducer is ground to a desired thickness in order to obtain a desired resonant frequency and a second electrode is applied to another surface of the piezoelectric body for connection to the high frequency supply.

Journal ArticleDOI
TL;DR: In this article, the authors discussed the generation of surface acoustic waves (SAW) on a biased electrostrictive substrate rather than a piezoelectric substrate, and two electrode structures were used: an interdigital pattern with an interleaving bias electrode, and a grating array pattern.
Abstract: The authors discuss the generation of surface acoustic waves (SAW) on a biased electrostrictive substrate rather than a piezoelectric substrate. Two electrode structures have been used: an interdigital pattern with an interleaving bias electrode, and a grating array pattern. Surface acoustic waves have been launched on strontium titanate and potassium tantalate niobate (KTN). The conversion efficiency and band-width of the transducers were measured for various electrode geometries. A theoretical relationship between the electrostrictive coefficient and the relevant photoelastic coefficient is derived and discussed, and experimental verification of the relationship is presented. The behaviour of the insertion loss of SAW on SrTi03 between 77 and 300K is described. Measurements of the dielectric permittivity and loss tangent of KTN between 10 Hz and 100 MHz and as a function of temperature are presented. It is concluded that SrTiO3 shows an induced piezoelectric effect large enough for device applications.

Journal ArticleDOI
TL;DR: In this article, a single piece of piezoelectric ceramic is placed in a non-uniform electric field and the surface deformation is calculated for periodic surface potential distributions on a simple geometric shape.
Abstract: Various applications require an optical mirror whose figure can be changed in a controlled manner as a response to an electrical input signal. This paper presents the theory of such a device, consisting of a single piece of piezoelectric ceramic situated in a nonuniform electric field. The surface deformation is calculated for periodic surface potential distributions on a simple geometric shape. Agreement with experimental results is good.

Patent
17 Mar 1975
TL;DR: In this paper, a piezoelectric pressure sensor for detecting the amount of oil in an engine oil pan of an automobile, and liquid level or amount of liquid such as water level in a water bath is presented.
Abstract: A piezoelectric pressure sensor for detecting the amount of oil in an engine oil pan of an automobile, and liquid level or the amount of liquid such as water level in a water bath, makes use of the phenomenon that an impedance of an excited piezoelectric element varies between in a gas and in a liquid. The pressure sensor is insensitive to surrounding temperature, and has high response and is of simple construction.