Effect of phase transition sequence on the ferroelastic domain structure of (NH₄)₃H(SeO₄)₂ at room temperature

Abstract

Temperature dependent evolution of ferroelastic domain structure in (NH₄)₃H(SeO₄)₂ was studied. It was found that ferroelastic domain structure exists in phases III, IV, V and VI. Ferroelastic domain pattern at room temperature depends on which phase IV or II the crystal was transformed to room temperature. Transformation from paraelastic phase I gives very fine domains with different, domain wall orientations which are difficult to determine. Transformation from phase IV to phase III gives a completely different picture of ferroelastic domain, domains are coarse with well defined orientations of their boundaries.