Raman Scattering and Phase Transitions in BaZnGeO₄ Crystal

Abstract

The polarized Raman spectra of BaZnGeO₄ crystal were measured at various geometrical arrangements corresponding to A(TO), E₁(TO)+E₁(LO) and E₂ representations over the temperature range 440°C∼−110°C, which covers the whole phases except for the phase I. In the low-frequency region below 300 cm⁻¹, the spectral feature varies depending upon temperature and a characteristic pattern of Raman spectrum for each phase is clarified. The spectral change due to the II–III phase transition appears continuous, in agreement with the second order nature. No spectral change is observed in the III–IV transition. The phase transition IV–V is clearly distinguished in the Raman spectra by an abrupt change of several bands and a thermal hysteresis, which reflects the first order nature.