Multiscale field-induced structure of (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 ceramics from combined techniques

The vast majority of studies on field-induced changes in (1-x)Pb(Mg1/3Nb2/3)O-3-xPbTiO(3) (PMN-xPT) materials at the morphotropic phase boundary (MPB) have been performed on single crystals, while the more complex responses in polycrystalline materials have not yet been resolved. By using combined microscopy and diffraction techniques, this study aims to determine the structural changes induced by application of an electric field to two representative MPB compositions of the PMN-xPT family, namely, PMN-30PT with the initial Cm and Pm coexisting phases, and PMN-35PT with the P4mm and Pm phases. Both ceramic compositions are characterized by a hierarchical domain structure with domains present at different length-scales. Based on the applied field measurements, major contributing effects in both compositions are outlined and discussed with respect to the processes related to the monoclinic phase and the adaptive phase theory. It is shown that the highly mobile domain walls are largely involved, along with the field-induced polarization rotation in the monoclinic PMN-30PT, and a phase transition to a mainly tetragonal structure in PMN-35PT. These multiscale results elucidate important aspects of field-induced changes in PMN-xPT materials, contributing to the understanding of the complex electrical and electromechanical response of relaxor ferroelectrics. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.