Brillouin scattering of high temperature phase transitions in LiKSO 4

A Brillouin study of LiKSO 4 has been performed in the temperature range 20–700°C. Discontinuous jumps in the temperature dependence of the Brillouin shifts appear at the transitions at 435°C and 670°C. In the intermediate phase (435°C < T < 670°C), two Brillouin modes are observed in the spectra of longitudinal acoustic waves propagating in the basal plane ([1 1 0] and [1 0 0] directions), suggesting the existence of crystallographic domains in this phase. The Brillouin spectra for [1 1 0] and [1 0 0] directions do not coincide in the intermediate phase, showing that this phase does not have the hexagonal symmetry, in disagreement with previous papers.