Micro-Brillouin Scattering of Relaxor Ferroelectrics with Perovskite Structure

摘要

Hypersonic elastic anomalies are investigated in ferroelectrics with perovskite structure by micro-Brillouin scattering to make clear the role of polar nanoregions (PNRs) and static random fields. In order to clarify the role of dynamic PNRs, the nearly second order normal ferroelectric phase transition is studied in 12 mol% KF substituted BaTiO_3 (KF-BT/0.12). The precursor elastic behaviors and the critical slowing down are clearly observed above the Curie temperature T_c. While in relaxor ferroelectric 0.93Pb(Zn_(1/3)Nb_(2/3))O_3-0.07PbTiO_3 (PZN-0.07PT) with PNRs and static random fields, below the intermediate characteristic temperature T~*, the suppression of slowing down of relaxation time is observed. The equation of stretched slowing down well reproduces the observed temperature dependence above T_C. The growth of the characteristic localized length of dynamic PNRs is estimated as a function of temperature.