The initial aging behavior of PZT ceramics

The planar coupling factor Kp generally decreases in aging process. However, an increase instead of decrease on Kp value is observed when thermal cycle is applied. It is believed that an internal stress is induced in the transverse direction of poling axis during cooling and forces the retrievable dipoles to arrange along the poling axis. The thermal induced internal stress (TIIS) results from the difference of thermal expansion coefficient between poling axis and its transverse. Normal aging mechanism plays the main role when the TIIS is relieved. The obtainable increase of Kp is dependent on the C/A ratio of perovskite lattice and correlated to the anisotropic thermal expansion