Phase Transition Behaviors in [011]-Oriented Pb(In1/2Nb1/2)O₃–Pb(Mg1/3Nb2/3)O₃–PbTiO₃ Single Crystals Studied by Dielectric and Micro-Brillouin Spectroscopies

Phase transition behaviors of unpoled and [011]-poled relaxor ferroelectric Pb(In 1/2 Nb 1/2 )O 3 –Pb(Mg 1/3 Nb 2/3 )O 3 –PbTiO 3 single crystals were investigated over a wide temperature range by dielectric and Brillouin scattering spectroscopies. The [011]-poled crystal exhibited two discontinuous dielectric and acoustic anomalies at ∼119 and ∼126 °C, which were attributed to two poling-induced structural phase transitions from rhombohedral to orthorhombic, and then to tetragonal symmetry. However, this poled crystal maintained the diffused phase transition behaviors of the unpoled one at higher temperatures above ∼126 °C. The disappearance of the poling effect upon the diffuse phase transition near the T C suggests that the macroscopic ferroelectric domains formed by poling are decomposed into mesoscopic and nano size polar regions at ∼126 °C. These polarization fluctuations and the coupling of these dynamic polar regions to the acoustic waves play the dominant role in the dielectric and acoustic anomalies, respectively. Therefore, a diffusive nature was commonly observed in both unpoled and poled single crystals near T C .