New Brillouin spectroscopy results in CsHSeO4 between room temperature andthe superionic transition

A Brillouin scattering investigation has been performed in CsHSeO4 from roo m temperature up to 120 degrees C, in a temperature range where a phase tra nsition was reported by some authors below the superionic one at 129 degree s C. For every elastic constant under study, a slight but unambiguous chang e of slope is found near 50 degrees C. The results are discussed in the lig ht of a recent LR reflectivity study. It is concluded that the Brillouin an omalies corroborate the existence of an additional phase transition between room temperature and the superionic one. (C) 2000 Elsevier Science Ltd. Al l rights reserved.