Raman Scattering of 0.91Pb(Zn_1/3Nb_2/3)O₃–0.09PbTiO₃Relaxor Ferroelectric Single Crystals

Abstract

Raman spectra were measured for lead zinc niobate-lead titanate solid solution 0.91Pb(Zn 1/3 Nb 2/3 )O 3 –0.09PbTiO 3 single crystals over a wide temperature range (-170–650°C) with different scattering geometry. Two phase changes were clearly observed by Raman scattering at the cubic to tetragonal ( T C–T ) and tetragonal to rhombohedral ( T T–R ) phase transition temperatures. The low-temperature transition related to the nanoregion behaviors has not been reported by other authors in the Raman scattering of other relaxor materials, and the mechanism was attributed to the increase in order at the B-site in 0.91PZN–0.09PT. High-temperature Raman spectra above T C–T with well-defined polarization are evidences that the Raman modes are mainly of the first order. The temperature dependence of the Raman modes above T C–T is due to the distorted space group of Fm3m associated with the positional disorder of Lead ion and the gradual disappearance of nanoregions with increasing temperature.