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 I Hz. At a frequency of 1 Hz, 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.