Phase transitions in CuInP₂(Se_xS_1−x)₆ layered crystals

Abstract

The low-frequency dielectric susceptibility of layered CuInP₂(Se_xS_1−x)₆ mixed crystals is investigated. The morphotropic phase boundary is found between x = 0.75 and 0.8. Broadening of phase transition anomalies in CuInP₂S₆ is observed at substitution of sulfur atoms by selenium. At substitution of selenium by sulfur in CuInP₂Se₆ a second order phase transition from the paraelectric phase to an intermediate phase is clearly observed up to the morphotropic boundary, while dielectric anomalies at the first order transition from the intermediate phase to ferrielectric phase are completely extinguished.

Key Words:

• Ferrielectrics
• morphotropic phase boundary
• dielectric properties