Role of internal field and exhaustion in ferroelectric switching

The role of internal field and exhaustion during ferroelectric switching was investigated by studying the dynamics of polarisation switching during the application of static electric fields at different points of the polarization-electric field (P-E) loop of a ferroelectric ceramic (PZT 5A). By simultaneously measuring polarization and strain changes during creep an insight into the evolution of the internal field during polarization switching was obtained. Electric field partial unloading tests were performed to estimate the magnitude of the effective internal field at different points of the P-E loop. Results show that the internal field increases proportionally with polarization reversal. A rate model that includes the effect of thermal fluctuations, internal field and exhaustion of nucleation sites during switching has been developed and applied to fit the polarization creep curves. The fitting of the creep curves in the sub-coercive region suggests that polarization hardening (increasing of internal field) is the mechanism controlling the polarization rate decay. At higher static applied electric fields the mechanism gradually changes and the exhaustion of the available nucleation sites becomes the main process responsible for the creep rate decay. (C) 2014 AIP Publishing LLC.