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

Ferroelastic reversible domain structure with ((2) over bar 03) 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 (10 (1) over bar) 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 similar to 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 ((2) over bar 03) twin is proposed.