Study of three different relaxor ferroelectrics by high resolution micro-Brillouin scattering

Three different relaxor ferroelectrics, 0.65PM-0.3PT, Sr0.61Ba0.39Nb2O6 (SBN), and Pb0.85La0.1Zr0.65Ti0.35O3 have been studied by Brillouin scattering using a microscope with a focal point of 1-2 mum. Relaxation modes have been directly observed for the first rime for all three samples. They form at a temperature much higher than the reported dielectric maximum temper ature T-m. Thermal evolution of the polar microregions has been illustrated by the temperature dependence of the relaxation lime. By scanning the microprobe over the 0.65PMN-0.35PT crystals, local distortions differing from the global symmetry were found due to microregions. A modified superparaelectric model has been proposed to describe the relaxation behavior in 0.65PMN-0.35PT. Comparison of the Raman and Brillouin results for SBN shows that the origins of relaxation modes are the dipolar relaxation associated with the polar vibration modes. Phase transition behaviors are discussed.