Evolution of the Polar Structure in Relaxor Ferroelectrics Close to the Curie Temperature Studied by Piezoresponse Force Microscopy

摘要

We present results of piezoresponse force microscopy studies on "uniaxial" relaxors Sr_xBa_(1-x)Nb_2O_6 (SBN) and on "cubic" relaxors Pb[Mg_(1/3)Nb_(2/3)]_(1-x)Ti_xO_3 (PMN-PT). The chosen compositions exhibit a spontaneous transition from the ergodic relaxor into the ferroelectric state. In both materials static regions of non-zero piezoresponse were found above the corresponding transition temperature. We attribute them to large polar nanosized regions (PNRs), which are "frozen" on the experimental time scale. The temperature evolution of the observed structures was investigated. It has been found that in PMN-PT these quasi-static PNRs are larger and exist in a broader temperature range than those in SBN.