Showing papers on "Piezoelectricity published in 1991"

(Bi1/2Na1/2)TiO3-BaTiO3 System for Lead-Free Piezoelectric Ceramics

Abstract: One of the (Bi1/2Na1/2)TiO3 (BNT)-based solid solutions, Ba-modified bismuth sodium titanate, (Bi1/2Na1/2)1-xBaxTiO3 (BNBT), is studied for its dielectric and piezoelectric properties as a new group of lead-free piezoelectric ceramics. A rhombohedral (Fα)-tetragonal (Fβ) morphotropic phase boundary (MPB) is shown to exist at x=0.06~0.07 by X-ray data, and dielectric and piezoelectric properties. BNBT ceramics with the MPB composition are superior as piezoelectric ceramics in high-frequency ultrasonic applications or as piezoelectric actuator materials because of a lower free permittivity, e33T/e0, and a high electromechanical coupling factor, kt or k33, along with high mechanical strength.

The extrinsic nature of nonlinear behavior observed in lead zirconate titanate ferroelectric ceramic

Abstract: The nonlinear electric and electromechanical responses of lead zirconate titanate Pb(ZrxTi1−x)O3 ceramics to an external ac electric field have been measured under different driving levels. The onset of measurable nonlinearity is observed to be accompanied by the appearance of hysteresis loops. This lossy nature suggests that the nonlinearities in a ferroelectric ceramic are generated by the domain‐wall motion. In addition, aging experiments and the bias field dependence of the threshold field (onset of nonlinearity) all indicate the extrinsic nature of the nonlinear behavior of ferroelectric ceramics. A phenomenological theory of Arlt, Dederichs, and Herbiet [Ferroelectrics 74, 34 (1987)] has been extended to include the nonlinear contributions. With only 90° wall vibration being considered, the theory leads to some basic understanding of the experimental results.

Stress induced shift of the Curie point in epitaxial PbTiO3 thin films

Abstract: A 50 °C shift in Curie temperature has been observed for c‐axis oriented PbTiO3 thin films using x‐ray diffraction. An analysis of the electrostrictive strain based on the Devonshire thermodynamic formalism showed that the shift in the Curie point for these films can be plausibly explained by an effective two‐dimensional compressive stress of ≊400 MPa. The single‐domain, single‐crystal dielectric susceptibility (η33) and piezoelectric coefficient (d33) were calculated and found to be relatively unaffected, at room temperature, by a compressive stress of this magnitude.

Drop-on-demand ink-jet printing head

Abstract: A drop-on-demand ink-jet printing head provided with an array of a plurality of piezoelectric elements arranged at regular intervals and fixed at their one ends to a base, the other ends of the respective piezoelectric elements being free ends which are disposed in opposition to nozzle respective apertures, the piezoelectric elements being formed by cutting, at predetermined width, a piezoelectric plate obtained by firing a lamination of paste-like piezoelectric material conductive material stacked alternately in layers. Since each piezoelectric element is composed of a thin piezoelectric plate interposed between electrodes, if a voltage of only about 30 V, which is sufficient to drive the thin piezoelectric plate, is applied across the electrodes, it is possible to largely flex the whole of the piezoelectric element. By this transformation, ink between the top end of the piezoelectric element and the nozzle aperture is discharged to the outside as an ink drop. Because the driving voltage required for forming an ink drop is as low as possible, it is possible to simplify a driving circuit, and because of cutting a piezoelectric plate, it is possible to form small-sized piezoelectric elements with the same accuracy as in a process of producing a semiconductor.

Ultrasonic probe system

Abstract: An ultrasonic probe system is disclosed, which is designed to allow connection of a DC power supply capable of applying a voltage higher than the coercive electric field of each of a plurality of piezoelectric layers thereto, and includes a polarization turn over circuit means for, when the DC power supply is driven, turning over the polarity of the DC power supply so as to direct electric fields of every two adjacent layers constituting the piezoelectric layers in substantially opposite directions or electric fields of all the layers in the same direction. When the polarization turn over circuit means turns over the polarity of a voltage to be applied to direct electric fields of every two adjacent layers of the piezoelectric layers in substantially opposite directions or electric fields of all the layers in the same direction, the polarization turn over circuit means performs control to apply the voltage during a blanking time of an operating time of the system, thereby performing conversion of a resonance frequency, and selectively generating ultrasonic waves having a plurality of different frequencies.

Longitudinal-effect type laminar piezoelectric/electrostrictive driver, and printing actuator using the driver

Abstract: A laminar longitudinal-effect type piezoelectric or electrostrictive driver which is displaced upon application of an electric field thereto. The driver includes laminar electro-mechanical converting elements each undergoes a displacement in a direction of the electric field due to the longitudinal mode of the reverse piezoelectric effect or the electrostrictive effect, and the temperature compensating elements each of which is interposed between the appropriate adjacent two laminar electro-mechanical converting elements. The temperature compensating elements have a higher coefficient of linear thermal expansion in the direction of the electric field or direction of displacement of the driver. The driver is suitably usable for an actuator for operating a print element of a printer, for example.

Piezoelectric/electrostrictive actuator having at least one piezoelectric/electrostrictive film

Abstract: A piezoelectric/electrostrictive actuator including a ceramic substrate, and at least one piezoelectric/electrostrictive actuator unit formed on at least a portion of at least one surface of the substrate, each piezoelectric/electrostrictive actuator unit having a first electrode film, a piezoelectric/electrostrictive film and a second electrode film which are laminated in the order of description, with the piezoelectric/electrostrictive actuator unit formed on the substrate by heat treatment.

Lateral field FBAR

Abstract: This invention is a design for lateral field film bulk acoustic resonators (LF-FBAR). All electrodes in this design are located on one surface of the piezoelectric material, thereby simplifying manufacturing and improving performance. The gap between electrodes is limited to a specified dimension to maximize the efficiency of the device. Single and multi-pole devices are described. Barium magnesium fluoride and lithium niobate are specified as the piezoelectric material for high frequency applications.

Piezoelectric ink jet printer head

Abstract: In a piezoelectric ink jet printer head having a laminated piezoelectric layer, actuating voltage is applied between only electrodes corresponding to a selected jetting device. A part of the piezoelectric ceramic layers between the electrodes is deformed in accordance with a slip effect, to jet ink from the selected jetting device. Since the polarization direction of the piezoelectric ceramic layers is almost perfectly perpendicular to the direction of an actuating electric field, the actuating voltage can be reduced. Further, piezoelectric ceramic layers can be stacked to obtain the necessary strength of a laminated piezoelectric element without decreasing the displacement amount. Thus, the reliability of the laminated piezoelectric element is enhanced. Moreover, the insulation of the electrodes is not deteriorated by a short circuit, migration of silver or the like. Such properties as durability and moisture resistance are also enhanced. Therefore, the printer head of the invention requires no components for preventing the deterioration of the insulation needed for prior art printer heads. The printer head can be thus made compact and lightweight, reducing the manufacturing cost.

Ferroelectric thin film ultrasonic micromotors

Abstract: Ferroelectric thin films of lead zirconate titanate (PZT) of morphotropic phase-boundary composition have been fabricated by a sol-gel spin-on technique for application to a new family of flexure-wave piezoelectric micromotors characterized by low speed and high torque. The high relative dielectric constant (1300) and breakdown strength (1 MV/cm) of the films lead to high stored energy densities. The piezoelectric coefficients d/sub 33/ and d/sub 31/ were measured to be 220 pC/N and -88 pC/N, respectively; the electromechanical coupling factors calculated from these data were k/sub 33/=0.49, k/sub 31/=0.22, and k/sub p/=0.32. The development of the piezoelectric ultrasonic micromotors from the PZT thin films and the architecture of the stator structure are described. Nonoptimized prototype micromotors show rotational velocities of 100-300 rpm and net normalized torques in the pN-m/V/sup 2/ range. >

Excitation of thin beams using asymmetric piezoelectric actuators

Abstract: In this paper, an approximate analytical model is developed for the excitation of a thin beam by a single piezoelectric actuator bonded to the surface of the beam The premise of this work is to investigate the excitation of beams by piezoelectric actuators on a more fundamental level than present work, and then use the asymmetric model to predict a wave response, rather than a modal response, on more complicated structure/actuator systems It is determined that the single surface mounted piezoelectric actuator simultaneously excites both flexural and extensional motion in beams whose relative amplitudes are functions of beam/actuator geometry and properties The model is then applied to the excitation of an infinite beam by two colocated arbitrarily driven actuators It is shown that this configuration can produce any desired combination of flexural and extensional waves in beams by varying the degree of asymmetry between the actuators

Accurate evaluation of the real and imaginary material constants for a piezoelectric resonator in the radial mode

Abstract: The standard IEEE procedure for determining the piezoelectric, dielectric, and elastic constants associated with the radial mode resonance of piezoelectric materials treats these constants as real rather than complex quantities. This approach is valid in the case of piezoelectric materials with low losses such as Lead Zirconate Titanate. However new lossy materials, such as ceramic-polymer composites, are becoming important to transducer designers. For such materials the losses can be taken into account by treating the constants as complex quantities. This paper presents a method to determine the complex form of the above constants. These constants are calculated from the experimental values of the first and second series resonance frequencies, the first parallel resonance frequency and appropriate half band frequencies and the low frequency admittance of the material, all of which can be measured on one disk sample. The method has also been used to automate the IEEE procedure for determining the...

Active control of noise transmission through rectangular plates using multiple piezoelectric or point force actuators

Abstract: This paper analytically demonstrates the use of multiple piezoelectric actuators bonded to the surface and point force actuators applied directly to a plate to reduce sound transmission through the plate. A harmonic plane wave incident on a simply supported, thin rectangular plate mounted in an infinite baffle was considered as the primary source. Both multiple piezoelectric and point force actuators are separately used as secondary (control) sources to attenuate the sound transmission through the plate. An optimal process was applied to obtain the input voltages of the piezoelectric actuators and the magnitude of the point forces, so that the radiated acoustic power can be minimized. Results show that a reduction of sound transmission through the plate is successfully achieved, if the proper size, number, and position of the piezoelectric or point force actuators are selected. Additionally, a comparison showed that point force actuators provide more effective control of the sound transmission than piezoelectric actuators; however, piezoelectric patches have more practical implementation than point force shakers, because of their low cost and light weight.

Wave Propagation in Piezoelectric Layered Media with Some Applications

Abstract: In this article we introduce a systematic methodology to investigate wave propagation in piezoelectric layered media. It is based on a matrix formalism and the con cept of the surface impedance tensor which relates the components of particle displace ment and the normal component of the electric displacement along a surface to the electric potential and the components of traction acting along the same surface. Once the surface impedance tensor for a single layer is calculated, a simple recursive algorithm allows the evaluation of the surface impedance tensor for any number of layers. As an example, the surface impedance tensor is used to find the dispersion curves for a bilaminated piezoelec tric plate. Also the dispersion curves for the subsonic interfacial waves when the plate is in contact with a nonconducting acoustic fluid is investigated. Floquet theory is also ap plied to study wave propagation when the layered medium is periodic.

Ultrasonic atomizing device

Abstract: An ultrasonic device for atomizing a liquid by the acoustic vibration generated with a vibrating plate (2) being mounted to a piezoelectric vibrator (1). The piezoelectric vibrator (1) consists of a piezoelectric ceramic and a pair of electrodes (P,Q) on the both end surfaces perpendicular to the thickness direction of the piezoelectric ceramic (30). The vibrating plate (2) has a lot of holes (22), and the area of the one of the openings of the hole is different with the area of the other. The piezoelectric vibrator (1) is efficiently vibrated under an application of an alternating current signal, whose frequency is almost equal to the resonance frequency of the piezoelectric vibrator (1). This vibration is transmitted to the vibrating plate (2), so that the vibrating plate (2) is also vibrated. A liquid existing at the part of the vibrating plate (2) is atomized through a lot of holes (22) formed in the vibratina olate (2).

The role of 90° domain wall displacements in forming physical properties of perovskite ferroelectric ceramics

Abstract: A proposed model which takes into account an elastic interaction between a polydomain grain and a surrounding ceramic matrix under weak external mechanical stresses has been used for evaluating a contribution from 90° domain wall displacements to piezoelectric and elastic constants of the perovskite ferroelectric ceramics. A difference between experimental and averaged constants of BaTiO3 ceramics can be explained by the estimated contribution.

Layered piezoelectric resonators with an arbitrary number of electrodes (general one-dimensional treatment)

Abstract: A general transfer matrix description for one‐dimensional layered structures consisting of piezoelectric and nonpiezoelectric anisotropic layers of arbitrary number is used to calculate the electrical admittance matrix for such resonators with N electrodes. The calculation is done in detail for linearly stacked resonators with two free surfaces as well as for ring resonators with a closed acoustical path. Experimental and theoretical results are given and compared for a ring resonator with two piezoelectric layers excited by four electrodes. Such a configuration can be used to generate unidirectional resonant waves.

Piezoelectric properties of GaAs for application in stress transducers

Abstract: In this paper piezoelectric stress transducers are proposed on the base of GaAs and AlxGa(1−x)As. These materials exhibit reasonable piezoelectric properties and since GaAs based integrated circuits have reached a high maturity they are a promising choice for integrated stress transducers. An additional feature of the high band‐gap material GaAs is its superior high‐temperature performance in comparison with Si. In this paper the piezoelectric and related properties of GaAs and AlxGa(1−x) are discussed. Therefore the piezoelectric tensors for the commonly used (100) and (111) oriented substrates are derived. These calculations are verified by measurements of some realized sensors using different substrate orientations.

Piezoelectric beams and vibrating angular rate sensors

Abstract: A tuning fork angular rate sensor made out of a single piece of quartz has been studied. The piezoelectric effect is used both to excite a reference vibration in the plane of the tuning fork and to detect a vibration normal to this plane. The amplitude of the second vibration is directly proportional to the applied angular velocity. The structure is made rigid in order for it to survive in a harsh environment. This implies that the only vibrationally active areas are the tines of the tuning fork. The performance of the sensor is predicted with the help of a phenomenological piezoelectric beam theory. This theory shows that it suffices to study the two-dimensional (2-D) dielectric field in the cross-sections of the beams in order to obtain the values of the piezoelectric equivalent components. Estimates of these values can be obtained without the use of special computer programs. The predictions are shown to be in agreement with measurements. >

Barrier height change in GaAs Schottky diodes induced by piezoelectric effect

Abstract: A novel manifestation of piezoelectric effects in GaAs has been observed. The change of barrier height, φB, of Schottky diodes induced by uniaxial stresses, S, along 〈100〉, 〈011〉, 〈011〉, and 〈111〉 has been measured. Shifts in φB due to the appearance of piezoelectric polarization charges at the semiconductor‐metal interface for directions other than 〈100〉 are observed.

Analysis of the electrically stimulated acoustic-wave method for observing space charge in semi-insulating films.

Abstract: The electrically stimulated acoustic-wave (ESAW) method for observing resident space charge in dielectric insulators has been used to characterize the poling behavior of millimeter-thick samples of polymeric insulation. The principle involves applying a voltage pulse across a material containing space charge and recording the exiting stress-wave signal by means of a piezoelectric transducer. This is a noninvasive technique and may be performed, in situ, during any space-charge-generating experiment. This method is able to detect space charge with a figure of merit equal to the sensitivity times the resolution of 130 pC/${\mathrm{cm}}^{2}$, and, to our knowledge, is the lowest reported for any nondestructive space-charge-profiling technique.

Piezoelectric shock wave generator

Abstract: A piezoelectric shock wave generator for use in medical equipment includes a plurality of piezoelectric elements being electrically interconnected to operate in parallel and mounted on a common carrier of curved configuration; a coupler medium couples shock waves as generated by these piezoelectric generators into the body of a living being, the improvement includes electrical insulation between the piezoelements being in fluid, ie liquid or gaseous state, in that each piezoelectric element is surrounded by the fluid in any direction towards any other piezoelectric element; the front ends of the piezoelectric elements may be physically separated, so that the coupler fluid and the isolating fluid are the same, and having a common flow space; alternatively, a membrane in front of all said piezoelectric elements provides electrical interconnection between them and physically separates the isolating fluid from the coupler liquid

Properties of Hydrophone with Porous Piezoelectric Ceramics

Abstract: We constructed a hydrophone using porous piezoelectric ceramics and conducted a detailed investigation into hydrophone sensitivity under higher pressure and its acceleration sensitivity as vibrational noise. At a pressure of 7.85 MPa, the hydrophone sensitivity of the porous piezoelectric ceramic hydrophone was some 20 dB higher than that of the piesoelectric ceramic hydrophones. The difference in acceleration sensitivity between the porous piezoelectric ceramics and the piezoelectric ceramics was extremely minor. The hydrophone sensitivity is sufficiently high to allow us to consider vibrational noise as negligible.

Influence of piezoelectricity on the photorefractive effect

Abstract: We demonstrate that the spatially modulated electric field that is associated with a photorefractive grating generates stress and strain components with symmetries that are different from those induced by a uniform electric field. Therefore, because of piezoelectricity and the elasto-optic effect, the symmetries of the effective dielectric and electro-optic constants to be used to describe the photorefractive effect differ from the symmetries of the usual dielectric and electro-optic tensors. We derive analytical expressions to be used to compute these new constants from the measured clamped and unclamped dielectric and electro-optic coefficients. Experimental evidence is presented.

Piezoelectric properties of layered perovskite A2Ti2O7 (A=La and Nd) single‐crystal fibers

Abstract: Lanthanum and neodymium titanate A2Ti2O7 (A=La, Nd) single‐crystal fibers were grown via the laser‐heated pedestal growth technique. The single‐crystal fibers were 600 μm in diameter and 3–4 cm in length. The piezoelectric, k23 and d23, and elastic compliance, s33, coefficients were measured using the standard resonance‐antiresonance technique. From a comparison of the measured coefficients to poled single crystal data in the literature, it is concluded that the La2Ti2O7 single‐crystal fiber grew in a single domain state.

Torsional force transducer and method of operation

Abstract: A transducer and method for imparting vibrational signals to a structure are disclosed. In one embodiment, a set of piezoelectric disks are constructed in conjunction with a deformable housing to impart controlled distortions to the structure, such as to a well pipe string. Torsional forces are applied to the structure due to the orientation of the piezoelectric material relative to the electric field applied thereto. The piezoelectric material is placed in layers, with the polarization axis orthogonal to the direction of the electric field. Alternate layers are oriented in opposing directions, and alternating electrodes are connected together, so that each layer cooperates with the others to twist the housing in the same direction. To improve transmission, the apparatus can be tuned to a frequency determined by a spectrum analysis of the pipe string. A reactance mass may be connected to the transducer to increase the amplitude of the imparted vibrations, and also to allow tuning of the frequency of vibrations of the transducer.