Asymmetric phase diagram of mixedCuInP2(SxSe1−x)6crystals

Abstract

Mixed ${\text{CuInP}}_{2}{({\text{S}}_{x}{\text{Se}}_{1\ensuremath{-}x})}_{6}$ crystals were investigated by broadband dielectric spectroscopy (20 Hz--3 GHz). The complete phase diagram has been obtained. The phase diagram of investigated crystals is strongly asymmetric---the decreasing of ferroelectric phase-transition temperatures in ${\text{CuInP}}_{2}{({\text{S}}_{x}{\text{Se}}_{1\ensuremath{-}x})}_{6}$ is much more flat with small admixture of sulfur than with small admixture of selenium. In the middle part of the phase diagram $(x=0.4--0.9)$ the dipolar glass phase has been observed. In boundary region between ferroelectric order and dipolar glass disorder with small amount of sulfur $(x=0.2--0.25)$ at low temperatures, the nonergodic relaxor phase appears. The phase diagram was discussed in terms of random bonds and random fields.