| Abstract: | Brillouin investigations have been performed over the temperature range 160-200°C, which includes the superionic phase transition near ~178°C. Strong discontinuities are obtained for the three elastic constants Cll, C22 and C33 at the superionic transition. In the superionic phase, two longitudinal Brillouin doublets can be observed for every direction of the acoustic wave vector. This fact can be attributed to the presence of two kinds of regions above the transition. Besides, systematic broadenings of these longitudinal lines are observed in the superionic phase. The results are qualitatively discussed in connection with theoretical expectations. |
