Asymmetric phase diagram of mixed $CuInP_2(S_xSe_{1-x})_6$ crystals

TL;DR

This study maps the phase diagram of mixed CuInP2(SxSe1-x)6 crystals, revealing an asymmetric ferroelectric to dipolar glass transition influenced by composition, with the discovery of a nonergodic relaxor phase at certain boundaries.

Contribution

It provides the first comprehensive phase diagram of CuInP2(SxSe1-x)6 crystals, highlighting the asymmetry and complex phases, including the nonergodic relaxor phase, based on broadband dielectric spectroscopy.

Findings

Asymmetric phase diagram with flat ferroelectric transition decrease for small S admixture.

Observation of dipolar glass phase in the middle of the phase diagram.

Identification of nonergodic relaxor phase at boundary regions.

Abstract

In this article mixed CuInP$_2$(S$_x$Se$_{1-x}$)$_6$ crystals were investigated by broadband dielectric spectroscopy (20 Hz - 3 GHz). From these results the complete phase diagram has been obtained. In the middle part of the phase diagram the dipolar glass phase has been observed. The phase diagram of investigated crystals is strongly asymmetric - the decreasing of ferroelectric phase transition temperatures in CuInP$_2$(S$_x$Se$_{1-x}$)$_6$ is much more flat with small admixture of sulphur then with small admixture of selenium. In boundary region between ferroelectric order and dipolar glass disorder with small amount of sulphur at low temperatures the nonergodic relaxor phase appears. The phase diagram was discussed in terms of random bonds and random fields.