Phase Transitions in CsH₃(SeO₃)₂ and CsD₃(SeO₃)₂

Abstract

Three phase transitions have been observed in CsD 3 (SeO 3 ) 2 using differential scanning calorimetry combined with measurements of the temperature dependence of the dielectric constant, lattice constants, and superlattice-reflection intensities. It is shown that a transition at -65°C reported for the first time corresponds to the antiferroelectric -128°C transition in CsH 3 (SeO 3 ) 2 . Two additional transitions in the deuterated compound were observed in the room-temperature range, both accompanied by pronounced thermal hysteresis. One of these phases may appear in a monoclinic modification, in contrast to the triclinic antiferroelectric and paraelectric phases.