A central peak in light scattering from the relaxor-type ferroelectric Na1/2Bi1/2TiO3

A complex perovskite-type single crystal Na1/2Bi1/2TiO3 (NBT) has been stud ied by Raman scattering. A broad central component has been revealed to ana lyze the temperature dependence of its intensity and width for the first ti me. The central component has features of a relaxation mode with the highes t intensity in the intertransition region, so it arises from a critical lig ht scattering on fluctuations of two coupled order parameters. The correlat ions between the central component behaviour, acoustic anomalies and dielec tric response as well as their relation to a model with competing interacti ons are discussed. It is suggested that the broad central peak component in light scattering is characteristic of the relaxer-type ferroelectrics with a sequence of phase transformation irrespective of whether transitions are really observed as in NET or whether transitions are frustrated under norm al conditions as in PbMg1/3Nb2/3O3 (PMN). (C) 2001 Elsevier Science B.V. Al l rights reserved.