This work investigates the evolution of micro-Raman spectra of a -oriented 0.67Pb(Mg1/3Nb2/3)O3-0. 33PbTiO3 single crystal in the temperature range from -120 to 200°C. For a poled sample, the Tlu mode splits into an E mode (remaining at 51 cm-1) and a new A1 mode (shifting to 95 cm-1 at -120°C) at the tetragonal to rhombohedral phase transition (Tc ∼ 70°C), while other modes remain the same. This A1 mode belongs to the rhombohedral phase. If the sample is depoled, this A1 mode persists for temperatures much above T c on heating, implying that local regions with rhombohedral symmetry still exist in the tetragonal phase. The underdevelopment of long-range order in the depoled crystal causes the sample to have typical characteristics of a relaxor while poling will enhance the long-range order to make it into a regular ferroelectric.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy (miscellaneous)