Showing papers on "Piezoelectricity published in 1986"

Piezoelectric resonators and their applications

Abstract: I. Introduction. II. Piezoelectric Materials and Their Elastic, Dielectric and Piezoelectric Properties. III. Vibrations of Piezoelectric Bars and Plates. IV. Approximate Solutions of Piezoelectric Plate Vibrations. V. Equivalent Electrical Circuit of a Piezoelectric Resonator. VI. Piezoelectric Resonators and Multi-Resonator Structures Used in Practical Applications. VII. Production Technology and Applications of Piezoelectric Resonators. References. Subject Index.

Piezoelectric shear wave resonator and method of making same

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.

Method of making piezoelectric composites

Abstract: Piezoelectric ceramic polymer matrices, piezoelectric composites, and methods of make the matrices and composites are disclosed.

Fluid property evaluation by piezoelectric crystals operating in the thickness shear mode

Abstract: Hydrodynamic coupling between a fluid and a planar piezoelectric crystal operating in the thickness shear mode provides a powerful, yet remarkably simple means to characterize fluid properties. Equations describing hydrodynamic coupling are developed for Newtonian fluids. This analysis takes into account, for the first time, the influence of a nonuniform piezoelectric crystal surface velocity. In particular, a Gaussian velocity distribution, suggested by other work, yields a functional relationship between hydrodynamic coupling and the fluid viscosity/density product that is in agreement with experiment. Beginning with these results, analytical methods for measuring individually the fluid visocity and density are described. Finally, it is demonstrated experimentally that the automatic gain control from the piezoelectric crystal oscillation circuit provides a ready means of fluid property characterization.

Dielectric, elastic and piezoelectric properties of porous PZT ceramics

Abstract: Porous ceramics with type 3–3 connectivity were prepared and investigated with a view to their application for ultrasound transducers. Ceramics with a porosity in the order of 0.4 to 0.5 exhibit sufficiently high permittivity (≈ 500), a thickness coupling factor equalling that of dense material (≈ 0.5), a low transverse coupling factor, a low vibrational Q (≈ 20) and low acoustic impedance (≈ 9·106kg/m2·s), all of which indicates their eminent suitability as a material for the fabrication of transducers as used in medical diagnostics. The experimentally determined influence of the porosity on the dielectric constants of these materials was used for the critical testing of various theories for calculating the constants of multiphase materials. It was found that the dielectric and elastic constants of porous piezoelectric ceramics can be very satisfactorily described on the basis of Bruggeman's theory, which has fallen somewhat into obscurity. Their piezoelectric properties are discussed with refer...

An experimental and theoretical study of 1–3 AND 1-3-0 piezoelectric PZT-Polymer composites for hydrophone applications

Abstract: A new type of piezoelectric PZT-polymer 1-3-0 composite was fabricated with a single large void present in the center of the composite. Experimentally and theoretically the addition of this type of void to a 1–3 composite significantly enhances the hydrostatic piezoelectric [dbar] h and [gbar] h coefficients. A comparison of the experimental results and theoretical predictions was made. The pressure and frequency dependences of the properties of the 1-3 and 1-3-0 composites were measured, along with the effect of hydrostatic pressure cycling. The 1-3-0 composites partially depoled from pressure cycling to 600 psi (4.1 MPa), indicating that the limit of hydrostatic sensitivity, physically possible for the soft PZT used, was exceeded.

Piezoelectric microwave resonator using lateral excitation

Abstract: An improvement in piezoelectric crystal resonators using lateral excitation whereby energy of vibration trapped in a region between the electrodes is provided by the inclusion of recessed electrodes adjacent a relatively raised piezoelectric region on at least one major face or surface of the crystal. The recessed electrodes oppose one another in either a horizontal or a vertical direction to generate a lateral field in the body of the crystal upon excitation. Additionally, curved edge interfaces are provided between the recessed electrodes and the piezoelectric crystal material to reduce field gradients. Tapered electrodes which have the effect of increasing the energy trapping in the gap between the electrodes are also disclosed.

Piezoelectric device for detection of polynucleotide hybridization

Abstract: A system for detecting polynucleotide hybridization. A polynucleotide is immobilized on a surface of a piezoelectric crystal. The resonance frequency of the piezoelectric crystal is measured through means for determining the resonant frequency of a piezoelectric crystal. A separate source of polynucleotide is exposed to the polynucleotide-coated piezoelectric crystal for a sufficient length of time and under conditions suitable for hybridization. The resonance frequency of the crystal is then again measured, and the difference between the resonance frequency before and after the incubation period will indicate the extent of hybridization.

Piezoelectric and Electrostrictive Actuators

Abstract: Recent developments in the areas of piezoelectric and electrostrictive actuators are reviewed: historical and theoretical background, newly-developed materials, applications and future problems are discussed. New materials such as lead zirconate titanate (PZT) based and lead magnesium niobate (PMN) based ceramics reveal excellent actuator characteristics especially by using wet-chemical preparation technique. Electrostrictive actuators are largely divided into three categories: servo displacement transducers, pulsedriven motors and ultrasonic motors. More than 20 practical applications are now under study, including deformable mirrors, cutting error compensation mechanisms, impact dotmatrix printers and surface-wave-type piezomotors. The remaining problem is reliability/durability of the actuators.

Piezoelectric ultrasonic transducer with acoustic matching plate

Abstract: A monolithic array ultrasonic transducer has a plurality of transducer elements formed thereon by isolating metallized areas on a piezoelectric plate without cutting the piezoelectric plate apart for each transducer element, and an acoustic matching layer having a longitudinal wave velocity within ±25% of a longitudinal wave velocity of the piezoelectric plate and a thickness equal to one half of that of the piezoelectric plate. The acoustic matching layer suppresses the radiation to an object of a partial wave in a direction of 60° to a normal line to the plane of the piezoelectric plate.

Elastic and piezoelectric coefficients of TSSG barium titanate single crystals

Abstract: For top seeded solution grown Barium Titanate single crystals in the tetragonal phase, the complete tensors of the elastic compliances, of the low frequency piezoelectric constants and of the coupling coefficients were determined. The method used was that of the piezoelectric resonator.

Evaluation of new piezoelectric composite materials for hydrophone applications

Abstract: Polymer-ceramic composites with different connectivity designs have been developed. The piezoelectric d and g coefficients of these composites in hydrostatic mode were characterized as a function of pressure, temperature, and frequency. All composite samples exhibited piezoelectric properties greatly improved over those of conventional piezoelectric ceramics. However, the introduction of soft polymer matrix caused the composite properties to be highly pressure-dependent. The effect of reinforced polymer matrix on the temperature and pressure dependences of the piezoelectric coefficients was also investigated. Prototype hydrophones containing the composite samples were designed and evaluated for their free-field voltage sensitivity. The potential use of polymer-ceramic composites for underwater acoustic applications is discussed.

Piezoelectricity, pyroelectricity and ferroelectricity in glass ceramics based on PbTiO3

Abstract: Piezoelectric, pyroelectric and ferroelectric glass ceramics of the PbOTiO 2 Al 2 O 3 SiO 2 system with the addition of other oxides have been studied. A piezoelectric resonance in a freely-suspended sample according to its thickness extension vibration mode is observed. The dielectric, piezoelectric, electromeemical coupling and other parameters, including d 33 = 40 × 10 −12 C/N, ϵ 33 T / ϵ 0 = 60, g 33 = 80 × 10 −3 m · V/N, k t = 0.225, are measured. The pyroelectric responses, with the characteristics p = (10−22)× 10 −9 C/cm 2 K, have good linearities from room temperature to nearly 200°C. The existence of ferroelectricity, which gives the most important precondition of the piezoelectricity and pyroelectricity after poling, is verified through: (1) the hysteresis loops by Sowyer-Tower circuit, (2) the ferroelectric domains by TEM, (3) the perovskite-type of ferroelectric crystalline phase PbTiO 3 solid solution by XRD, (4) the abnormality of transition between ferroelectric phase and paraelectric phase, as well as (5) the normalized mode based on an IR absorption band referred to the ferroelectric soft mode of Ti I bond stretching vibration. This material is different either from the corresponding ceramics and single crystals or from non-ferroelectric polar glass ceramics and isotropic gglass ceramics containing ferroelectric crystalline phases. The new characters and features have also been discussed.

Composite Piezoelectric Materials for Medical Ultrasonic Imaging Transducers - A Review

Abstract: This paper surveys published research on the use of composite physicians. piezoelect.ric materials to make the acoustic transducers used in medical ultrasonic imaging. For medical imaging transducers, attention has focused on the 1-3, PZT-rod/polymer composite structure. The piezoelectric plates used in such ultrasonic transducers consist of a polymer matrix which holds together parallel thin rods of piezoelectric ceramic oriented perpendicular to the faces of the plate. By varying the properties, proportions and spatial scales of the polymer and piezoceramic constituents a rich variety of material properties are achieved. Of particular interest for medical imaging transducers is the ability to engineer materials whose electromechanical coupling is higher than that of conventional materials and whose acoustic impedance is close to that of tissue. Besides these basic advantages in material parameters. composites have properties that facilitate meeting other technological requirements. Flexible composite piezoelectrics can be formed into complex curved shapes for steering and focusing the acoustic waves. Transducer arrays can he made from composites by patterning the electrode alone -- cutting the piezoelectric is not required.

Method and apparatus for measuring viscosity in a liquid utilizing a piezoelectric sensor

Abstract: A piezoelectric element energized to exhibit thickness-shear mode vibration is utilized to measure the viscosity of liquids. Electrodes, of an inert material are bonded to the major faces of the disc shaped crystal and are of a lesser diameter than the crystal surfaces so as to provide a concentric ring area of the crystal that is unenergized.

The dynamics of a thin piezoelectric cylinder gyroscope

Abstract: The paper considers the theory of a new type of vibratory rate gyroscope. The design considered is based upon a thin cylindrical shell of radially polarized lead zirconate titanate on which are dep...

Nonlinear piezoelectricity and electrostriction of alpha quartz

Abstract: Starting from the rotationally invariant nonlinear equations of electroelasticity the initial derivative of the propagation velocity of elastic waves with respect to the magnitude of an electric biasing field is derived. This derivative is given by an expression which is linear in third‐order material constants. From propagation measurements of ultrasonic waves under the application of a constant electric field, values for the eight independent components of the nonlinear piezoelectric tensor eKABCD and for the eight independent components of the electrostriction tensor lKLAB for alpha quartz are obtained. While some of the electrostriction constants remain rather uncertain, the nonlinear piezoelectric constants are determined with good accuracy.

Dielectric and Piezoelectric Properties of Nylon 9 and Nylon 11

Abstract: Various specimens of nylon 9 and nylon 11 were prepared, and their crystalline structures, the temperature and frequency dependences of electric properties were investigated. Dielectric constants (at 10 Hz).of various specimens were about 2.5—3 in the temperature range from −160°C to room temperature, and they began to increase near Tg and reached above 30 at about 100°C. They showed three dielectric loss peaks due to two types of local mode motion and the glass transition. Piezoelectric behavior of the α form specimen obtained by slow cooling of melts and that of the γ form specimen obtained by casting from its trifluoroacetic acid solution were almost the same, but a mixture of α and γ forms obtained by quenching of the melts into liquid nitrogen had a larger piezoelectric constant than the above two. From these results it may be considered that the lower regularity in the dipole orientation within the mixture makes it relatively easier to rearrange the dipoles in parallel to the electric field in the poling process. Nylon 9 had a larger piezoelectric constant than nylon 11, which may be due to the higher dipole density of nylon 9. The piezoelectric stress constant of the stretched film was larger than the unstretched one, but the piezoelectric strain constant of both were similar. The largest piezoelectric stress constant of 2.1 mCm−2 (at 25°C) was obtained from a stretched nylon 9 specimen and the largest piezoelectric strain constant of 1.1 pCN−1 (at 25°C) was obtained for nylon 9 specimen which was a mixture of α and γ forms.

Experimental verification of distributed piezoelectric actuators for use in precision space structures

Abstract: An analytic model for structures with distributed piezoelectric actuators is experimentally verified for the cases of both surface-bonded and embedded actuators. A technique for the selection of such piezoelectric actuators' location has been developed, and is noted to indicate that segmented actuators are always more effective than continuous ones, since the output of each can be individually controlled. Manufacturing techniques for the bonding or embedding of segmented piezoelectric actuators are also developed which allow independent electrical contact to be made with each actuator. Static tests have been conducted to determine how the elastic properties of the composite are affected by the presence of an embedded actuator, for the case of glass/epoxy laminates.

A Two-Dimensional Theory for High-Frequency Vibrations of Piezoelectric Crystal Plates with or Without Electrodes

Abstract: Two‐dimensional equations of motion of successively higher‐order approximations for piezoelectric crystal plates with triclinic symmetry are deduced from the three‐dimensional equations of linear piezoelectricity by expansion in series of trigonometric functions of the thickness coordinate of the plate. These equations, complemented by two additional relations: one, the usual relation of face tractions to the mass of electrodes, and the other relating face charges to face potentials and face displacements, can accommodate either the traction and charge boundary conditions at the faces of the plate without electrodes or the traction and potential boundary conditions at the faces of the plate with electrodes. Dispersion curves are obtained from the first‐ to fourth‐order approximate plate equations for a rotated 45° Y‐cut lithium tantalate plate without electrodes, and these curves are compared with those from the frequency equation of the three‐dimensional equations with close agreement. Solutions of force...

A lattice model of the thickness-mode piezoelectric transducer

Abstract: Abstmct-The development of a new three-port model of the thickness-mode piezoelectric transducer, employing linear systems theory, is presented. A discrete bidirectional lattice is used to describe mechanical wave propagation and continuous transfer functions to represent the electrical parameters. When presented in block-diagram format, an extremely valuable insight is gained into the nature of piezoelectric interaction. The lattice concept is extended to the analysis of multilayered structures and, when implemented in the discrete time domain, close agreement with experimental data is obtained. A number of experimental and simulation results are included for comparison. I. INTRODUCTION ONVENTIONAL models of the thickness-mode piezoelectric transducer invariably utilize transmissionline analogs in which the electromechanical properties of the system are evaluated by means of electrical network concepts. Examples of this include the equivalent circuits of Mason [l] and the more recent KLM [2] model, which uses a center-tapped transmission line to model acoustic wave propagation. In this form both models are also readily adapted for the analysis of multilayered transducer structures. However, electrical analogs possess some disadvantages which limit their flexibility when applied to piezoelectric transducer modelling [3]. Physical insight into the nature of the transduction process is often masked, and as a'result the influence of external electrical and mechanical load conditions on transducer behaviour is difficult to determine. To overcome this, an alternative strategy has been proposed by Hayward [3] who adopted a systems feedback approach to

Method for selective filtering of a fluid using porous piezoelectric material

Abstract: A filter which is particularly useful with biological material is formed of porous piezoelectric material such as PZT or Polyvinylidene fluoride. By an application of a voltage to the piezoelectric material, the filter body is caused to vibrate so as to inhibit fouling. In a modification, the piezoelectric material is not itself porous but is bonded to a filter membrane such that vibrations of the piezoelectric material are transmitted to the membrane. Through suitable control of the vibration, the selectivity of the filter can be controlled. In other modifications the vibratory movement of the filter membrane can be produced in other ways such as electro-mechanically.

Piezoelectric copolymer jacketed single‐mode fibers for electric‐field sensor application

Abstract: Characteristics of a piezoelectric copolymer jacketed optical fiber are presented. The jacket consisting of a copolymer of vinylidene fluoride and trifluoroethylene was made piezoactive by corona poling. The performance of the fiber as an optical‐phase modulator was demonstrated over a frequency range of 20 Hz–5 kHz. An electric field‐induced phase shift of 1.5×10−7 rad/(V/m) per meter of fiber was measured in the low‐frequency (axially unconstrained) region. Several resonance peaks in optical phase shift were observed and discussed in conjunction with piezoelectricity in polymer jackets.

Method and apparatus for generating low frequency acoustic energy waves

Abstract: An acoustic transmitter is employed in a borehole logging tool for generating low frequency acoustic energy waves. A tube of piezoelectric material is sealed at both ends and filled with liquid. A pliable boot surrounds such piezoelectric tube. At least one passageway communicates the inside of the piezoelectric tube with the inner surface of the boot. Differing electrical polarities are applied to the inner and outer surfaces of the piezoelectric tube. These electrical polarities are modulated to excite the piezoelectric tube to resonate at a frequency controlled by the inertia of the liquid in the passageway and the mass of the liquid inside the piezoelectric tube.

Broadband piezoelectric ultrasonic transducer for radiating in air

Abstract: A piezoelectric ultrasonic transducer for radiating ultrasonic energy in the medium of air has a number of piezoceramic ultrasonic radiators disposed in registry within a dimensionally stable carrier block which has an intrinsic acoustic impedance which is lower by a factor of at least eight than that of the piezoceramic material and which has a high mechanical attenuation 1/Qm greater than approximately 0.05. The carrier block is yieldable at at least one closed face thereof for emission and/or reception of ultrasonic energy. The piezoelectric transducer elements may be divided into a number of side-by-side elements which may be individually energized, or may have electrodes connected in series for energizing the individual transducer elements in common. The combined operation of the ultrasonic transducer elements within the carrier block results in an ultrasonic transducer having broadband characteristics matched for ultrasonic transmission in the medium of air of short ultrasonic waveforms and for receiving ultrasonic energy for near-distance detection.