PRECURSOR DYNAMICS OF Pb(B1/2B′1/2)O3-TYPE RELAXOR FERROELECTRICS STUDIED BY BROADBAND MICRO-BRILLOUIN SCATTERING

Abstract

This paper reviews the recent progress in the understanding of the dynamics of Pb(B1/2B′1/2)O3 -type relaxor ferroelectrics using of broadband micro-Brillouin scattering spectroscopy, which covers a large frequency range from 1 to 1000 GHz by a tandem multi-pass Fabry–Perot interferometer. In contrast to Pb(B1/3B′2/3)O3 -type relaxors, there is no frustration on the B-site of perovskite structure and the degree of order of B-site cations depends on heat treatment. Remarkable softening of sound velocity and an intense central peak are observed above the Curie temperature TC owing to the polarization fluctuations in polar nanoregions (PNRs). Unlike the Pb(B1/3B′2/3)O3 relaxors, Pb(B1/2B′1/2)O3 does not undergoes a typical diffuse phase transition without lead vacancies on A-site which enhances random fields. For the (1-x) Pb ( B 1/2 B ′1/2) O 3–x PbTiO 3 solid solutions, the long range polar order increases as the PbTiO3 content increases. Nevertheless, a central peak owing to dynamic PNRs still remains even for the composition near the MPB, and a critical slowing down is clearly observed in the vicinity of TC.