Polarized Raman spectroscopy study of phase transitions in 0.915Pb(Zn1/3Nb2/3)O3-0.085PbTiO3 relaxor ferroelectric single crystals

A complex perovskite 0.915Pb(Zn1/3Nb2/3)O-3-0.085PbTiO(3) solid solution with remarkable ferroelectric and related properties was studied by microprobe Raman scattering in a wide temperature range from 70 K to 580 K and in two different polarizations. The specimen chosen was in single crystal form and the spectra were recorded in both its parallel and perpendicular backscattered configurations. The spectra were complex due to short-range ordering on the B-site. It was established mat the Raman spectra of the cubic phase is of the first-order in nature and is associated with the local structural distortions. The integrated intensities of the low frequency (50 cm(-1)) and high frequency (780 cm(-1)) bands were shown to exhibit the anomalies at the points of structural phase transitions. However, two phase transitions were determined corresponding to the cubic (C) to tetragonal (T) and from T to rhombohedral (R) structure with the former quite obvious and the later less apparent. The results were explained well by a description of change in ordered nanoregions existing at B- site almost at all temperatures.