Dayu Zhou

Rate dependence of soft PZT ceramics under electric field loading

Polarization and longitudinal strain of the commercial soft PZT piezoceramic PIC151 were measured as a function of amplitude and frequency of an AC electric field. The range of frequencies considered was selected in the quasi-static range from 0.01Hz to 1.0 Hz. The electric field was selected as triangular loading. Besides the standard hysteresis loops for polarization (P) and strain (S) versus electric field (E), strain versus polarization curves (S-P curves) were plotted in separate diagrams. It was shown that both polarization and strain were frequency dependent. The coercive field increased with the loading frequency. Furthermore, a significant hysteresis was observed for S-P curves at a loading frequency below 1Hz. At a frequency of 1Hz, however, the S-P plots were nearly close to an idealized parabolic curve without hysteresis. A tentative explanation shall be given for these observations in terms of the rate effects of the domain switching process.

High-field dielectric and piezoelectric performance of soft lead zirconate titanate piezoceramics under combined electromechanical loading

Piezoelectric actuators normally have complicated structures and work under severe loading conditions, e.g., high driving electric field and significant compressive preload. This study is focused on the experimental investigation of the electromechanical properties of a commercial soft lead zirconate titanate material under loading conditions simulating the in-service environment of high-strain actuators. The polarization and strain responses were first measured under a constant-stress preload. A significant enhancement of the dielectric and piezoelectric performance is observed within a small prestress range. At much higher preload levels, the predominant mechanical depolarization effect makes the material exhibits hardly any piezoeffect. In the other two series of tests, the specimen was subjected to cyclic mechanical load with different mean stresses and amplitudes. When the stress is applied in-phase with electrical loading, the polarization and strain outputs are found to monotonically decrease with ...

Determination of room-temperature creep of soft lead zirconate titanate piezoceramics under static electric fields

This study focuses on the experimental investigation of the time-dependent effects of a commercial soft lead zirconate titanate material at room temperature. Samples in initially unpoled states were subjected to a cyclic stepwise electric field which was kept constant at different levels for 300 s. Due to ferroelectric domain switching, significant nonlinearity and hysteresis were observed in the overall polarization and strain response. In particular, the material exhibited creep behavior as the applied electric field was held constant over extended periods of time. This creep was caused by microscopic domain switching processes induced gradually during the holding time. The creep was of primary or transient type in nature and depended strongly on the magnitude of the load applied. Most pronounced creep was observed when holding the field close to the coercive field. Logarithmic representation of the polarization or strain versus time curves indicated that the creep behavior could be quantified approxima...

Experimental investigation of domain switching criterion for soft lead zirconate titanate piezoceramics under coaxial proportional electromechanical loading

In this experimental work, “soft” lead zirconate titanate specimens in an initially unpoled state were subjected to combined electromechanical loading, in which a compressive stress and a parallel, proportional electric field were applied simultaneously. By changing the ratio of stress to the electric field between tests, a series of nonlinear polarization and strain responses were obtained. An attempt has been made to explain the experimental findings by simultaneously taking into account the contributions of dielectric response, elastic deformation, piezoeffects, and irreversible domain switching. Initial domain switching surfaces in the biaxial stress and electric field space were determined based on an offset method. Several switching conditions existing in the literature were summarized and compared with the experimental data obtained in this work. Such an investigation may serve to calibrate and validate existing constitutive models concerning the large-signal nonlinear behavior of piezoceramics.

Multi-axial non-proportional polarization rotation tests of soft PZT piezoceramics under electric field loading

In this experimental work, multi-axial, non-proportional polarization rotation tests were performed for a commercial soft PZT material under purely electric field loading. Large pre-poled piezoceramic plates were cut into rectangular blocks of size 15mm × 5mm × 5 mm, with their long axes inclined at a set of angles (from 0° to 180°, in steps of 15°) to the initial poling direction. After cutting, the top and bottom 5mm × 5 mm surfaces were electroded with a thin layer of silver paint and then, a ramp-shaped electric field was applied to cause the polarization to change. In addition to the polarization measurement along the field loading direction, the normal strain responses in all three coordinate directions were monitored simultaneously using strain gauge technique. Based on a series of polarization and strain versus electric field curves, switching (domain reorientation threshold) surfaces were constructed in the bi-axial electric field plane using the conventional offset method. The experimental data can be used to examine the existing switching criteria in phenomenological models for the non-linear constitutive behavior of piezoceramics.

Experimental Studies on the Non‐linear Ferroelectric and Ferroelastic Properties of Piezoceramics

We summarize some of the experimental work on the constitutive behaviour of Soft‐PZT piezoceramics carried out at the Research Center Karlsruhe during the recent years. In particular, multi‐axial, non‐proportional polarization rotation tests are presented for a commercial soft PZT material under purely electric field loading. In addition to the polarization measurement along the field loading direction, the normal strain responses in all three coordinate directions were monitored simultaneously using a strain gauge technique. Based on a series of polarization and strain versus electric field curves, switching (domain reorientation threshold) surfaces were constructed in the bi‐axial electric field plane using the conventional offset method. The experimental data can be used to examine the existing switching criteria in phenomenological models for the non‐linear constitutive behavior of piezoceramics.