Hydrostatic Piezoelectric Constants Research Articles

Design and Implementation of Digital Piezoelectric Constant Testing System

Digital piezoelectric constant testing system was designed in this paper, which was based on hydrostatic test method. The system is composed of hydrostatic device, charge amplifier circuit, peak holding circuit, A/D calibration circuit, data processing by DSP. Pressure-release value is obtained by digital pressure transmitter on the hydrostatic device. Combining with mean filtering and A/D calibration, DSP can sample accurate voltage signal. Considering the difference between the equivalent circuit of charge amplifier and its practical circuit, the calculated hydrostatic piezoelectric constant is in better agreement with the theoretical value. The experiment results show that the accuracy of testing system is less than 4%.

Design of Hydrostatic Piezoelectric Constant Testing System

A new testing method for hydrostatic piezoelectric constant, dh , was studied in this paper. This testing system consists of five parts, which are hydrostatic simulator, signal acquisition and processing circuits, data acquisition, serial communication interact circuit, data processing and display. Researched the method of signal acquisition for hydrostatic piezoelectric charge, designed the charge amplifier circuit, signal processing circuit as well as the data acquisition and serial communication interact circuit with microcomputer, programmed for the date acquisition and processing system software. The hydrostatic piezoelectric constant, dh , of piezoelectric ceramic samples were tested. The experimental results showed that this new testing method is available. The new testing system is characteristic of manipulation simply and low cost.

Effects of Lateral Stress on the Electromechanical Response of Ferroelectric Ceramics: Experiments versus Model

Mechanical depolarization is an important cause of failure in piezoelectric actuators and sensors. In this paper, the effects of one-dimensional lateral pressure on the linear and nonlinear behavior of PZT ceramics were experimentally studied. The experimental results show that the lateral pressure can change the crystal symmetry of the ceramic from 1mm to mm2. A domain-switching model dividing each 180 switching to two successive 90 switching is proposed to explain the experimental results. Finally, based on the experimental results, a simple design is proposed to prevent piezoelectric sensors from mechanical depolarization. Meanwhile, the simple design is apt to increase the hydrostatic piezoelectric constant of the piezoelectric marine sensors, thus enhancing their sensitivity.

Piezoelectric composites with 3-3 connectivity by injecting polymer for hydrostatic sensors

Three kinds of polymer materials, with varying hardness, were injected into porous PZT fabricated by the conventional sintering process to form a PZT/polymer composite with the majority of 3-3 connectivity. Such properties as the dielectric constant, the coupling factor, and the hydrostatic piezoelectric constants were studied. The effect of the polymer hardness on the properties of the composites also was investigated. Although the porous PZT exhibited much higher hydrostatic piezoelectric coefficient than conventional PZT and PZT/polymer composite, it is fragile for the processes such as silver pasting, electrical poling, and so on. The PZT/Polymer composite demonstrated a more promising mechanical strength than porous PZT. The mechanically soft polymer showed less degraded effects on the hydrostatic piezoelectric coefficient than the hard polymer.

Effects of porosity and polymer matrix on the properties of piezoelectric ceramic/polymer composites

Porous PZT was fabricated by conventional sintering process in the present study. Three kinds of polymer materials, with varying hardness, then were injected into the porous PZT to form a PZT/polymer composite with 3–3 connectivity. Such properties as the dielectric constant, the coupling factor, and the hydrostatic piezoelectric constants were characterized. The effect of the polymer-phase hardness on the properties of the composites also was investigated.

Improving hydrostatic performance of 1-3 piezocomposites

Type 1-3 piezocomposites consist of aligned piezoelectric rods embedded in a passive polymer matrix and have better hydrostatic behavior than single-phase piezoelectric materials. The improved hydrostatic performance of 1-3 piezocomposites comes from two major effects: the axial stress amplification and the lateral stress reduction in the piezoelectric rods. An improved micromechanical model has been developed to predict the hydrostatic response of 1-3 piezocomposites and to examine the interaction between the piezoelectric rods and the polymer matrix. Effective hydrostatic piezoelectric constants for the composite are predicted and compared to those calculated using a generalized plane strain model. The influence of matrix stiffness, interlayer stiffness, rod aspect ratio, and rod volume fraction on the load transfer and the effective hydrostatic piezoelectric coefficient was investigated. The results obtained provide quantitative information on how various parameters affect the hydrostatic response of the composites.

BaTiO3 Particle-Size Dependence of Ferroelectricity in BaTiO3/Polymer Composites

BaTiO3 particle-size dependence of ferroelectricity in BaTiO3/polymer composites was investigated from the viewpoints of the crystal phase in BaTiO3 powder and piezoelectric properties in BaTiO3/polymer composites. The crystal phase of BaTiO3 powder was transformed from tetragonal to pseudocubic at a critical particle size of 0.1 to 0.2 µm at room temperature. The piezoelectric charge constant (d33) and hydrostatic piezoelectric constant (dh) were obtained through poling treatment, although their values were small in BaTiO3/polymer composite using the pseudocubic BaTiO3 powder.

Piezoelectric Properties of 0-3 Composite of Polymer and Ceramic Powder Mixture of PZT and PbTiO3

Hydrostatic piezoelectric constants of composites consisting of polymer and ceramic powder mixture of PZT and PbTiO3 with different average ceramic particle sizes (PZT/PT=7.5 µm/3.3 µm) took enhanced values in the PZT-rich region of the ceramic powder mixture at 70 ceramic volume percent. The reasons are discussed in this paper.

Piezo- and pyroelectric properties of poly(vinylidene fluoride) under high pressure

Abstract Pressure and temperature dependences of piezoelectric constant, hydrostatic piezoelectric constant, pyroelectric constant, dielectric constant, electrostriction constant, film thickness, Poisson's ratio, Gruneisen constant and volume of crystal of poly(vinylidene fluoride) have been observed. Using these data and assuming two kinds of expressions about dielectric constant e c and spontaneous polarization Psc of crystal, the composite model theory has been discussed. It was found that the use of Weiss type for e c and Psc gives reasonable results.

The piezoelectric properties of some PZT composites

Abstract Two types of PZT/polymer composites were investigated. The first is a coral-type PZT having a 3-3 connectivity, produced by the simplified BURPS technique. The second type is an epoxy-PZT composite with a 3-2, connectivity. Properties including the dielectric constant, dissipation factor and the hydrostatic piezoelectric constants were characterized. The effects of temperature and pressure on these properties were also studied.

Pressure dependence of the piezoelectric polarization of LiNbO3 and LiTaO3

Abstract Linear and nonlinear hydrostatic piezoelectric constants for lithium niobate and lithium tantalate are determined from measurements of the hydrostatic piezoelectric polarization at pressures from 0.05 GPa to 2.6 GPa. The nonlinear constants are found to be large and relatively easy to detect. In LiTaO3 the nonlinear constant is large enough to reduce the piezoelectric coefficient to zero in the vicinity of 2.2 GPa. The nonlinear constants are interpreted in terms of the pressure dependence of the electrostrictive constants. The linear constant measurements indicate that LiNbO3 should prove useful for a wide variety of piezoelectric stress transducers for impulsive loading measurements.

Pressure-induced reversal of the sign of the hydrostatic piezoelectric constant of lithium tantalate

Measurements of the piezoelectric polarization of lithium tantalate for hydrostatic pressures up to 26 kbar show that the hydrostatic piezoelectric constant decreases smoothly to zero at a pressure of 22 kbar. Above this pressure the piezoelectric constant smoothly changes sign. This is believed to be the first observation of such an effect.