Showing papers on "Piezoelectricity published in 1985"

Ultrasonic generating system with feedback control

Abstract: An ultrasonic generating system for coupling vibrating energy into a load, such as living tissue, has been described which employs a piezoelectric crystal having excitation electrodes on opposite faces thereof A feedback electrode is disposed on one face of the crystal adjacent to and insulated from one of the excitation electrodes to provide a feedback signal between the feedback electrode and the other excitation electrode A power supply is provided for applying excitation energy to the excitation electrodes The feedback signal is utilized to slave the frequency of the power supply voltage to the resonant frequency of the crystal and to disable the power supply when the impedance of the load applied to the crystal rises above a predetermined level

A Piezoelectric Ultrasonic Motor

Abstract: A piezoelectric ultrasonic motor is constructed by tightly contacting a rotor to a piezoelectric ultrssonic resonator with eliptical vibrstion (PUREV). The PUREV successfully operated with a torsion coupler in which a torsional mode coupled with a bending mode is excited by the same frequency longitudinal vibration. The typical values of the present motor are 120 r.p.m. with no load, and 90 r.p.m. with a load of 13 kg-cm, under a 40 kHz/100 volt sinsoidal voltage, i.e. 12 watts with 80% efficiency. These values correspond to a high output power density of 80 W/kg over the limit value 30 W/kg expected in the ordinary motors.

Anisotropy of Fracture Toughness of Piezoelectric Ceramics

Abstract: The anisotropy of fracture toughness of PZT- and barium titanate-based piezoelectric ceramics was studied using doubletorsion and indentation methods. The influence of elastic anisotropy and the piezoelectric effect in calculating the Kc value are discussed. The fracture toughness in the polarization plane is greater than that in the perpendicular plane. A model is suggested to explain the observed anisotropy; it is based on assumption of a stress-induced domain reorientation zone near the crack tip.

Method of making a piezoelectric shear wave resonator

Abstract: An acoustic shear wave resonator comprising a piezoelectric film having its C-axis substantially inclined from the film normal such that the shear wave coupling coefficient significantly exceeds the longitudinal wave coupling coefficient, whereby the film is capable of shear wave resonance, and means for exciting said film to resonate. The film is prepared by deposition in a dc planar magnetron sputtering system to which a supplemental electric field is applied. The resonator structure may also include a semiconductor material having a positive temperature coefficient of resonance such that the resonator has a temperature coefficient of resonance approaching 0 ppm/°C.

Piezoelectric resonating device

Abstract: The present invention provides a piezoelectric thin-film resonator comprising a non-piezoelectric film layer formed on a substrate, a lower electrode, a piezoelectric film layer and an upper electrode. An air-gap layer is formed between the non-piezoelectric film and the substrate to facilitate vibration of the piezoelectric film layer at the resonate frequency. The resulting resonating device is mechanically strong while at the same time being capable of operating at high frequency.

Elastic, Piezoelectric, Acousto-Optic and Electro-Optic Properties of Li2B4O7

Abstract: Transparent, core-free and good quality single crystals of Li2B4O7 have been successfully grown by the Czochralski method. All dielectric, elastic and piezoelectric constants, and their first- and second-order temperature coefficients have been determined by measuring resonant and antiresonant frequencies of bars and plates with various orientations. The theoretical and experimental results show the potential usefulness of Li2B4O7 for bulk wave or SAW applications. Further, measurements on optical, acousto-optic and electro-optic properties of Li2B4O7 have also been carried out.

Surface acoustic wave devices and method of manufacture thereof

Abstract: A phase and amplitude compensated surface acoustic wave (SAW) structure is described in which computer controlled compensation is achieved by laser chemical etching of selective portions of a compound chemical film deposited on the surface of a piezoelectric SAW substrate in the path of propagation. The compound film comprises a layer of amplitude attenuating cermet material formed on the substrate and a phase compensating layer of molybdenum formed over the cermet material and in contact with the substrate surface.

Effects of crystal structure on piezoelectric and ferroelectric properties of copoly(vinylidenefluoride‐tetrafluoroethylene)

Abstract: Piezoelectricity and ferroelectricity in 80 mol % vinylidene fluoride/20 mol % tetrafluoroethylene copolymers (VDF‐TFE) were measured at various crystallinities. In order to control the crystallinity, the crystallization pressure was varied from 1 bar to 5 kbar. All the samples prepared by this method contain only form I crystals but with various crystallinity and crystal thickness. Especially, a band structure characterizing an extended chain crystal was observed in the sample crystallized under more than 4 kbar. Remanent polarization (Pr) obtained by the D‐E hysteresis curve increases with the crystallinity, and the extrapolated Pr of 126 mC/m2 nearly coincides with the value of 140 mC/m2 calculated from the unit cell dimension and dipole moment. The coercive field (Ec) decreases with the crystallinity. This would be explained by the expansion of intermolecular distance and a decrease in the number of folds, which affect the rotation of dipoles under an electric field.

Unusual pyroelectric and piezoelectric properties of fresnoite (Ba2TiSi2O8) single crystal and polar glass-ceramics

Abstract: The dielectric, piezoelectric and pyroelectric properties of fresnoite (Ba2TiSi2Os) single crystal and polar glass-ceramics were studied in the temperature range - 150 to 200°C. The sign of pyroelectric coefficient is positive at room temperature and becomes negative at 190°C. The dielectric constant, pyroelectric coefficient and planar coupling coefficient show a maximum value at 160°C and the frequency constant shows a minimum at the same temperature. The probable reasons for the anomaly in these properties are discussed.

Pyroelectric and Piezoelectric Properties of Lithium Tetraborate Single Crystal

Abstract: Pyroelectric. piezoelectric and dielectric properties of single crystal Li2B4O7 (LTB) are measured in the temperature range from 50°C down through -150°C. At room temperature LTB has dielectric constant K3~10 (at 100 KHz) and dielectric tan δ~1 (10 KHz). At liquid nitrogen temperatures, the tan δ decreased to ~10-3. Pyroelectric coefficient at room temperature measured ~30 µC/m2-K which increased to -120 µC/m2-K at -150°C and showed the pyroelectric figure of merit p/K comparable to the value obtained on TGS at room temperature. Primary and secondary components of pyroelectricity are separated and the results suggest that the major contribution comes from the primary effect in Li2B4O7. Piezoelectric measurements show high values of g33270×10-3 V-m/N and gh100×10-3 V-m/N indicating potential application of Li2B4O7 in the area of pressure sensors.

Photostrictive Actuator Using PLZT Ceramics

Abstract: Photostriction explainable by the superposition of the bulk photovoltaic effect and piezoelectricity has been investigated in the solid solution ceramics of (Pb, La)(Zr, Ti)O3. Using the optimum composition PLZT(3/52/48), we have fabricated a photodriven relay as a trial photostrictive actuator. Though the response is rather slow, we have observed primitive relay function controllable by the optical irradiation.

Piezoelectric composite material

Abstract: A piezoelectric composite material prepared by compounding a ferroelectric ceramic powder comprising microcrystals having virtually single domains and a polymer. This composite has both the high piezoelectric property of the ferroelectric ceramic and the pliability of the polymer.

Temperature Compensated Piezoelectric Lithium Tetraborate Crystal for High Frequency Surface Acoustic Wave and Bulk Wave Device Applications

Abstract: All dielectric, elastic and piezoelectric constants, and their first and second order temperature coefficients have been newly determined. Based upon these data set, Rayleigh SAW, leaky SAW and bulk wave properties have been studied for the various orientation and propagation from theoretical and experimental points of view. Both theoretical and experimental results have shown that Rayleigh SAW possesses a particularly useful cut with the zero temperature coefficient of delay (ZTCD) at (oO,~~O,~OO). A new temperature-compensated leaky SAW orientation has been located around (Oo,750,750) with vs of 4120m/s and k = 1.6%. Further it has been conf irmedj, theoretically

Piezoelectric electro-acoustic transducer

Abstract: A piezoelectric transducer is formed by fixedly laying a second oscillating plate over a first oscillating plate to which a piezoelectric oscillating assembly having a piezoelectric oscillating element is adhered, so as to define an acoustically sealed space. And, as the first oscillating plate oscillates by being driven by the oscillation of the piezoelectric oscillating assembly, the second oscillating plate oscillates by being driven thereby by way of the sealed space. Due to the shifting of the resonance frequencies of the piezoelectric oscillating assembly and the first and the second oscillating plates, and also due to the restriction of the oscillation by the sealed space, a wide frequency property is obtained, making this piezoelectric transducer particularly suitable for use as a speaker or as a microphone.

Equilibrium polarization and piezoelectric and pyroelectric coefficients in poly(vinylidene fluoride)

Abstract: A calculation of the equilibrium polarization and of the piezoelectric and pyroelectric coefficients of β‐phase poly(vinylidene fluoride) (PVF2) is presented. The effects of both the orthorhombic crystal structure and of the finite separation between the monopoles of the molecular dipole are taken into account. Good agreement is obtained with the experimentally measured polarization and piezoelectric and pyroelectric coefficients of β‐PVF2 films.

Theoretical Equations for Dielectric and Piezoelectric Properties of Ferroelectric Composites Based on Modified Cubes Model

Abstract: This paper describes mainly theoretical considerations for the dielectric and piezoelectric constants of ferroelectric composite types 1–3, 0–3 and 3–0. There is a newly derived theoretical equation for the piezoelectric d31 constant of 1–3 type parallel model, which is distinguished from that of the conventional 2–2 type parallel one. The dh-equation of the 0–3 type piezorubber composites, ellipsoidal ceramic particles arrangement in the PVDF-PZT composites, and the porosity dependencies of the dielectric and piezoelectric constants of porous ceramics are discussed based on the modified cubes model.

Piezoelectric ultrasonic transducer with flexible electrodes adhered using an adhesive having anisotropic electrical conductivity

Abstract: An ultrasonic transducer includes a piezoelectric member consisting of either a unpolarized piezoelectric polymer material or the like, or an in-advance polarized piezoelectric polymer material or the like, a first flexible substrate on which a first electrode set and their connecting leads are formed, these being bonded to one surface of the piezoelectric member, and a second flexible substrate on which a second electrode and its connecting lead are formed, these being bonded to the other surface of the piezoelectric member, wherein the piezoelectric member is sandwiched between the first electrode set and second electrode. The electrodes can apply a voltage to polarize the unpolarized piezoelectric polymer material in a manufacturing process of the piezoelectric member, or apply a drive voltage to the finished ultrasonic transducer. Also disclosed is a method of manufacturing the ultrasonic transducer.

High accuracy determination of real and imaginary parts of elastic, piezoelectric and dielectric constants of ferroelectric PLZT (11/55/45) ceramics with iterative method

Abstract: A new measurement system for determination of real and imaginary material coefficients of piezoelectric ceramics is presented.The method of calculation, the hardware, the software and the accuracy are discussed, and measurements of SE11, d31, eT33, SD33, g33, βT33, CD33, h33, βS33 of a piezoelectric ceramic, with the composition (Pb, La).89,.11(Zr, Ti).55, .45O3 are shown. This material is investigated in a temperature range from -50°C to + 27°C in which it shows a transition from a ferroelectric to an uncertain (maybe penferroelectric) phase. It is found that 'mg33 has a sign reversal at the phase transition.

Polymeric piezoelectric ultrasonic probe

Abstract: There is disclosed a polymeric piezoelectric ultrasonic probe using a polymeric piezoelectric member which comprises a polymeric piezoelectric member; a common electrode formed on one surface of the polymeric piezoelectric member; and electrodes for driving provided as opposed to the common electrode with the polymeric piezoelectric member being interposed therebetween, the electrodes for driving being formed on a polymeric thin film. The polymeric piezoelectric ultrasonic probe of the present invention has advantages that not only breaking or short circuit of electrodes shaped in rectangular strips can be prevented, but also it becomes possible to connect lead wires with good reliability. Besides, not only cumbersomeness is registration of electrodes shaped in rectangular strips during lamination of polymeric piezoelectric members can be cancelled, but also acoustic-electrical coupling or cross-talk can be reduced.

Multilayer Piezoelectric Ceramic Actuators and Their Applications

Abstract: A piezoelectric ceramic actuator, with low driving voltage and high energy conversion efficiency, has been fabricated by the tapecasting method. It has many layered structure internal electrodes, connected electrically in parallel. Operation is based upon a piezoelectric stiffened effect. For an acrtuator 9 mm in length and with 2×3 mm cross sectional dimensions and 115 µm gaps between individual internal electrodes, 6.6 µm free displacement and 18.7 kgf clamping force can be obtained, when applying DC 100 V. It has been confirmed that the actuator is useful for a miniaturized light polarization control system and high performance impact matrix printer head.

Underwater piezoelectric arrangement

Abstract: Underwater piezoelectric arrangement in which it comprises two piezoelectric elements made of piezoelectric ceramic-polymer composites and juxtaposed to form a single layer structure, one of the element(s) having larger hydrophone constant than that of the other element(s), and by noise cancelling of the piezoelectric assembly there can be selectively detected only charges or voltages generated by acoustic waves which acts on each element.

Barium Titanate Ceramics with High Piezoelectricity Fabricated from Fibrous Particles

Abstract: Barium titanate ceramics with high degrees of c-axis orientation were fabricated from fibrous particles. The maximum piezoelectric constant, d33, obtained was ≅270 pC/N, which is much higher than values reported previously.

Ultrasonic transducer using piezoelectric composite

Abstract: An ultrasonic transducer using a piezoelectric composite in which a plurality of piezoelectric poles are arranged in matrix maintaining a gap and a polymer is charged into the gap. The piezoelectric poles are arranged maintaining a pitch which is shorter than a wavelength of a sound wave at a fundamental resonance frequency of the transducer in a medium. Further the pitch may be changed in a direction in which the piezoelectric poles are arranged, in order to restrain the grating lobe from generating.

New Piezoelectric Materials for Ultrasonic Transducers

Abstract: Two types of piezoelectric ceramics with large electromechanical anisotropies (planar coupling factor kp is much less than thickness dilatational coupling factor kt) have been developed for use as high-frequency ultrasonic transducer materials: modified lead titanate ceramics (Pb, Sm)(Ti, Mn)O3 and ferroelectric PbZrO3 ceramics modified by adding small amounts of Pb(Mn1/3Nb2/3)O3 and PbTiO3. These new ceramics have a large kt and kt/kp. PZT/polymer piezoelectric composite sheets have also been developed for use in medical transducers. These composite sheets were fabricated using a "dicing and filling" technique. The resulting composites are highly flexible and show both a large kt and a low acoustic impedance.

Studies on the nonlinear piezoelectric response of polyvinylidene fluoride

Abstract: Simple mechanical models can be useful in investigating the structural dependence of the piezoelectric activity of uniaxially oriented polyvinylidene fluoride. An experimentally observed strong nonlinear relationship between the mechanical load and the transverse piezoelectric coefficient d32 is presented. This new behavior is discussed on the basis of a parallel arrangement of crystalline and amorphous regions perpendicular to the orientation axis. The coefficient d32 changes its sign also, the deformation being less than 3% in all cases. A mechanical series model is applied for the coefficient d31 whose behavior is very linear with the applied mechanical load. Furthermore, d32 shows a significant time dependence after a change in the mechanical load applied. These nonlinear effects depend upon structural features such as crystal perfection and were attributed to processes occurring in the crystalline regions and in their interfaces with the amorphous surrounding, respectively. Also, the technical import...

Piezoelectric properties of a porous PZT ceramic

Abstract: A porous PZT material from a Japanese source was characterized for its piezoelectric properties. Initial values of 82 pC/N for the hydrostatic d constant and 0.046 Vm/N for the hydrostatic g constant were observed. The material also showed no pressure hysteresis effect upon pressure cycling. In order to improve its poor mechanical strength due to high porosity, the material was modified by an epoxy coating and by epoxy impregnation. The effect of these modifications was shown to alter the piezoelectric properties from those of the untreated samples, and, in addition, to introduce a large pressure hysteresis effect. Sample variations were found among different experimental batches, and the dependence of their piezoelectric properties on sample thickness was determined. These variations may be attributed to sample inhomogeneity resulting from powder packing and the degree of poling.

Reinforced piezoelectric transducer and pressure sensor using such a transducer

Abstract: A piezoelectric transducer including a polarized piezoelectric material film, which also has a reinforcing material incorporated into the mass and which prevents any deformation of the film in certain given directions. The invention also relates to a pressure sensor using such a transducer. This sensor can be used both as a pressure sensor and as a pressure gradient measuring device.

Piezoelectric filler and flexible piezoelectric composites

Abstract: A piezoelectric ceramic powder comprises a solid solution of PbTiO 3 and BiFeO 3 wherein a portion of the iron content is replaced with manganese. A piezoelectric ceramic-polymer composite of 0-3 connectivity is disclosed using as the piezoelectric filler the manganese-doped solid solution.

Piezoelectric and pyroelectric polymers

Abstract: Disclosed are new piezoelectric/pyroelectric materials of polarized homopolymer and copolymers of trifluorovinyl acetate. Also disclosed is a unique predictive relationship for determining the piezoelectricity of unknown material.