Study of the low-frequency Raman scattering in NaNbO₃crystal

Abstract

The Raman scattering spectrum of the sodium niobate crystal, in both P and R phases, has been investigated from room temperature up to 440°C. The dependence of the low-frequency (LF) spectrum clearly reveals, for the first time, over a wide temperature range, the presence of a strong quasi-elastic scattering below a LF zone centre phonon. The phase transition mechanism is discussed, considering an order–disorder process induced by the relaxation of the Nb ions.