Temperature-dependent mechanical depolarization of ferroelectric ceramics

Abstract

Mechanical depolarization of poled lead titanate zirconate (PZT) ceramics was conducted at a series of temperatures from 25 to 180 °C in a temperature-controlled silicon oil tank. Both the longitudinal strain and polarization of the bar-shaped PZT samples were measured during uni-axial compression up to 400 MPa. It is found that both the stress-induced switchable polarization and the switchable strain of the poled PZT samples decrease steadily with increasing temperature. Unpoled PZT samples were also tested and the switchable strains follow a rule similar to the poled ones but of smaller magnitude. By measuring the P–E hysteresis loops, polarization variations and strain variations of a compression-free, poled PZT sample during a full cycle of heating–cooling, it is found that at elevated temperatures, the reduced switchable polarization by stress is caused by the pyroelectric effect and the reduced switchable strain is mainly due to the decreasing tetragonality (c/a). Furthermore, it was found that both the poled and unpoled PZT ceramics show a recoverable thermal shrinkage effect within the measurement temperature range.