Phase transition behaviors in relaxor ferroelectric [001]-poled Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals studied by Brillouin light scattering and dielectric spectroscopies

Phase transition behaviors of [001]-oriented Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) single crystals were studied under unpoled and [001]-poled conditions by Brillouin light scattering and dielectric spectroscopies. The unpoled crystal showed a diffused elastic anomaly accompanied by substantial dielectric dispersion, which were associated with the temperature evolution of polar nanoregions represented by the excitation of strong central peaks. The poled crystal exhibited two-step changes in both dielectric and elastic properties, which were attributed to the successive phase transitions from rhombohedral to tetragonal, and then from tetragonal to cubic phase upon heating. The high-temperature tetragonal-cubic phase transition remained diffused with dielectric dispersion due to local random fields inherent in relaxors. The transverse acoustic mode disappeared at the rhombohedral-tetragonal phase transition indicating a clear symmetry change