Rate-dependent ferroelectric switching in barium titanate ceramics from modified PUND experiments

Predicting and controlling the rate-dependent electro-mechanical switching in ferroelectric ceramics is challenging due to our current lack of understanding the underlying domain switching mechanisms at short time scales or high rates. Therefore, we propose an experimental protocol, which is a modification of the so-called Positive Up Negative Down (or PUND) experiment, to probe the rate-dependent competition between domain nucleation, domain growth, and variant selection in barium titanate ceramics as a representative material. Our experiments use a pump electric field pulse to switch the sample from a poled state at electric field rates spanning five orders of magnitude ( 10−2−102 MV/m ⋅ s). The remanent microstructures at the end of different pump pulses are probed using a subsequent probe electric field pulse, which is applied at a constant quasistatic rate. Results reveal reduced polarizability at higher electric field rates, indicating reduced domain switching. In addition, this pump-probe experiment shows an increase in domain wall nucleation vs. growth at higher rates. Simultaneous mechanical strain measurements using stereographic digital image correlation indicate a difference in nucleated domain wall variants while switching anti-parallel vs. parallel to the pre-poled direction. The data shows that ferroelastic 90° domain nucleation is preferred in the former case, while ferroelectric 180° nucleation is preferred in the latter. Our study highlights the importance of quantifying microscopic kinetics of domain nucleation, domain wall growth, and the effect of mobile defects in modeling the short-time electro-mechanical response of ferroelectric ceramics.