Isotope Effect of Monoclinic Rb(D_1−xH_x)₂PO₄ on the Phase Transitions

Abstract

Dielectric constant along the b axis of crystals in monoclinic Rb(D_1−xH_x)₂PO₄ system was measured in a temperature range from −190°C to 160°C. Phase diagram of the system obtained in a range between x=0 and 0.8 shows a relatively large isotope effect on the III–II phase transition with a shift of its transition temperature to higher temperature for the decrease of x, and a small isotope effect on the II–I phase transition but with a shift of its transition temperature to lower temperature for the decrease of x.