Study of monoclinic-tetragonal-cubic phase transition in Pb (Zn _1/3 Nb_2/3) O₃ -0.08 PbTiO₃ single crystals by micro-Raman spectroscopy

The relaxor ferroelectric Pb (Zn_1/3 Nb₂/3) O ₃ -0.08 PbTiO₃ (PZN-0.08 PT) single crystal has been investigated using polarized micro-Raman scattering technique in a wide temperature range from -150 to 350 °C. Raman spectra of the crystal at temperatures lower than 90 °C show 11 modes over a frequency range of 100-1000 cm-1. There are 12 Raman active vibration modes in the monoclinic structure of relaxor ferroelectrics according to the group theory analysis. Thus the structure of PZN-0.08PT single crystal at low temperatures is confirmed as monoclinic. Two structural phase transitions in the crystal were observed when the temperature was increasing. First, the monoclinic-tetragonal (M-T) phase transition happens at 90 °C. Second, the tetragonal-cubic (T-C) phase transition takes place at 170 °C. © 2009 American Institute of Physics.