Micro-Brillouin Scattering and Central Peaks of 0.91Pb(Zn 1/3 Nb 2/3 )-0.09PbTiO 3 Single Crystals

Central peaks and acoustic phonons of 0.91Pb(Zn 1/3 Nb 2/3 )-0.09PbTiO 3 (0.91PZN-0.09PT) relaxor single crystals have been studied in detail by a micro-Brillouin scattering technique. Two phase transitions from cubic to tetragonal and tetragonal to rhombohedral upon cooling are observed through the frequency shifts and damping of the acoustic phonons. 0.91PZN-0.09PT near morphotropic phase boundary is heterogeneous, and the heterogeneity is studied by scanning the incident laser spot over the crystal sample. Elastic constant c 33 and sound velocity v LA are determined. Central peaks have been directly observed, they show marked temperature dependence both in intensity and width; they are closely related to the fluctuations of polar microregions. Relaxation times are obtained and the mechanisms of central peaks are discussed.

Keywords:

• Brillouin Scattering
• Central Peak
• Relaxor Ferroelectric
• Lead Zinc Niobate
• Elastic Constant
• Sound Velocity