Time dependence of mechanical depolarization in ferroelectric ceramics

Piezoelectric PZT-ceramics exhibit the common feature that their piezoelectric response to electrical or mechanical stresses increases nonlinearly with the amplitude of the applied stress. This nonlinear increase is commonly interpreted in terms of domain wall motion. Thus for piezoelectric actuators based on this type of material the achieved displacement is not only due to the intrinsic piezoelectric effect, as observed in single domain crystals, but also to orientation processes of ferroelectric domains. While the quasistatic ferroelectric and ferroelastic properties of PZT are well known, there are only few published measurements concerning the dynamic behaviour of PZT-materials under large signal operation. In this paper a measurement method is presented, which allows the time dependence of mechanically induced domain processes to be studied. From such measurements, a comparison between the transient behaviour of various PZT compositions under different applied stresses is made. The transient force and charge responses from a stress-step is examined within the time range between 10 milliseconds and 60 seconds. Lastly it is also shown, that there is a fundamental difference in the transient response of donor-doped and acceptor-doped PZT ceramics.