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

Abstract

We present results of piezoresponse force microscopy studies on “uniaxial” relaxors Sr _x Ba_{1− x} Nb₂O₆ (SBN) and on “cubic” relaxors Pb[Mg_1/3Nb_2/3]_{1− x} Ti _x O₃ (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.

Keywords:

• Relaxors
• piezoresponse force microscopy
• single crystals
• phase transition

Acknowledgments

Financial support by the Deutsche Forschungsgemainschaft (Schwerpunktprogramm “Strukturgradienten in Kristallen”) and by KBN (grant 4 T08A 007 25) is gratefully acknowledged. One of the authors (V.V.S.) acknowledges financial support from the Portuguese Science and Technology Foundation (FCT) through a postdoctoral fellowship grant.