High-Temperature Phase Transition in RbH₂PO₄

Abstract

Dielectric and thermal measurements were carried out for the RbH₂PO₄ crystal belonging to the tetragonal system at room temperature. The RbH₂PO₄ crystal, which could be obtained by heating the tetragonal RbH₂PO₄ crystal above the tetragonal-monoclinic transformation temperature, undergoes successive phase transitions at 390.1K and 248.8K. The tetragonal-monoclinic transformation is accompanied by a rearrangement of hydrogen bonds, namely, a change from a three-dimensional network of hydrogen bonds in tetragonal RbH₂PO₄ to a two-dimensional network in monoclinic one. The tetragonal space group {I\bar{4}2d} changes to the monoclinic P2₁/c by passing through the transformation temperature.