Direct observation of the domain kinetics during polarization reversal of tetragonal PMN-PT crystal

Lead magnesium niobate-lead titanate (PMN-PT) solid solutions are intensively studied for the last two decades due to their outstanding piezoelectric properties. However, despite the strong interest, there is a lack of studies of domain kinetics and domain structure evolution, which are of great importance for the development of domain engineering in PMN-PT. We present the results of the domain kinetics study during polarization reversal in tetragonal PMN-PT single crystals by in situ optical visualization accompanied by analysis of the switching current. Three types of domain structure evolution have been revealed: (1) formation and growth of macroscopic a-domains, (2) formation of charged domain walls as a result of intersections of macroscopic a-domains, and (3) formation and growth of c-domains. The domain wall motion velocities were estimated. It has been shown by comparison of the switching current and optical one that the main switching current peak is related to the growth of c-domains, whereas the small one is caused by the capacitive input of the charged domain walls. The enhancement of dielectric permittivity by two orders of magnitude due to the appearance of the charged domain walls has been revealed. The difference of forward and reverse polarization reversals was attributed to the clamped switching conditions.