Ferroelastic domain structure in the vicinity of superionic phase transition in CsDSO₄ crystals

Abstract

Ferroelastic reversible domain structure with (203) and (101) domain walls is induced in CsDSO₄ crystals by [100] and [001] compression at room temperature. About 3–4 K below the superionic phase transition new (101) domain walls appear in the crystal. Changes in the wedge-shaped domain pattern are observed also in (100) cut samples at temperature 3–4 K below T_s, both on heating and on cooling (with thermal hysteresis of ∼ 7 K). The changes of the domain pattern in the close vicinity of T_s are related to an anomaly in thermal expansion along the [001] direction reported at (T_s-3K) by Dilanyan and Shekhtman. Molecular model of the (203) twin is proposed.