Diffuse Phase Transition of 0.8Pb(Ni1/3Nb2/3)O3-0.2PbTiO3 Single Crystals Studied by Micro-Brillouin Scattering

Brillouin scattering in the relaxor ferroelectric 0.8 Pb(Ni 1/3 Nb 2/3 )O 3 -0.2 PbTiO 3 has been studied in the temperature range from −150°C to 500°C. The anomalies of the frequency shift and full width at half maximum of Brillouin component at the structural phase transition from the paraelectric to ferroelectric phases have been successively detected. The origins of the anomalies of them are discussed from the phenomenological point of view. The central peak caused by the fluctuation of polarization has been also observed in the VV and VH scattering geometries with the large free spectral range of 150 GHz. It is found the difference of central peak intensity obtained in VV and VH scattering geometries.