Kinetics of ferroelectric switching in poled barium titanate ceramics: Effects of electrical cycling rate

Our understanding of the rate-dependent electro-mechanical response of ferroelectric ceramics is incomplete - primarily due to limited experimental data characterizing the material behavior at high rates (or short time scales). Therefore, we experimentally study the effect of cycling rate on polarization switching in poled barium titanate (BaTiO3) ceramics across five orders of magnitude in cycling rate. Mechanical strain data as a function of the applied electric field were collected across three orders of magnitude. We quantify the rate-dependent coercive field, remanent and peak polarization, apparent permittivity and apparent piezoelectric coefficient, and actuation strain. Results reveal a reduction in polarizability of the material with increasing rate and a strong asymmetry in the electromechanical hystereses, which comes with differences in the rate dependence when loading parallel vs. anti-parallel to the direction of poling. Supported by a simple model and ex-situ piezoresponse force microscopy, we conclude that rate effects arise from the mobility of 90. domain walls and the competition between nucleation and growth of domains. The asymmetric hysteresis highlights the importance of point charge and dipole defects, which affect the domain wall kinetics and hence the rate effects of polarization switching through the competing time scales of space charge migration, dipole reorientation, and domain wall activity.