Phase transitions and dielectric properties of mixed NH₄HSeO₄-NH₄HSO₄ crystals

Abstract

A number of NH₄HSeO₄-NH₄HSO₄ mixed crystals have been grown. The system exhibits limited solubility in the solid state. The limiting solid solutions correspond to x = 0.32 and 0.67 (x - molar fraction of NH₄HSO₄). Based on X-ray diffraction, Differential Thermal Analysis and dielectric studies, the phase diagram has been drawn with x as the parameter. It has been found that crystals with 0.9 ≥ x ≥ 0.67 do not show a ferroelectric phase transition and resemble dipole glasses in their properties.