Electric field and temperature-induced phase transition in Mn-doped Na _1/2Bi_1/2TiO₃-5.0 at.%BaTiO₃ single crystals investigated by micro-Raman scattering

A micro-Raman scattering technique was used to investigate the electric-field and temperature dependent phase stability of Mn-doped Na _1/2Bi_1/2TiO₃-5.0at. %BaTiO₃ single crystal. The Ti-O mode was found to exhibit a slight shift at a low electric field (E = 10 kV/cm) and splitting at higher electric field (E≥ 30 kV/cm), ascribed to field-induced local distortion and phase transition, respectively. The temperature-dependent Raman scattering was also measured over a wide range of 150-800 K to study the phase stability of poled samples. A new Raman mode at about 200 cm^-1 and an anomaly in intensity of the Ti-O modes were detected at 390 K, indicating a ferroelectric to antiferroelectric phase transition. The frequency shift of TiO₆ octahedral modes implied a transition to a paraelectric state at 550 K. Furthermore, the Ti-O and TiO₆ octahedral modes were found to be sustained in the high-temperature paraelectric state.