Light scattering spectroscopy of relaxor ferroelectrics

Abstract

Raman scattering was studied in model relaxor ferroelectrics PbSc_1/2Ta_1/2O₃PST) and PbMg_1/3Nb_2/3O₃(PMN) (both single crystals) and in related low-permittivity materials SrAl_1/2Ta_1/2O₃ (SAT), SrAl_1/2Nb_1/2O₃ (SAN) and BaMg_1/3Ta_2/3O₃ (BMT) (all ceramics). A comparative analysis of the Raman spectra suggests that these complex perovskites consist of nanoscale clusters with the 1:1 B-site order, irrespective of (1:1 or 1:2) B cations stoichiometric composition. This result is in agreement with the recent microstructure studies of both PST and PMN, by direct methods. The low-permittivity compounds reveal the basic static spectrum corresponding to 1:1 or 1:2 composition, which is modified in relaxors by dynamic effects in the course of evolution to the ferroelectric state. PST and PMN clearly show such dynamic effects as mode broadening and a central peak.

Keywords:

• Raman scattering
• relaxor ferroelectrics