Evidence of network demixing in GeS 2–Ga 2S 3 chalcogenide glasses: A phase transformation study

Abstract

The information of phase transformation is attained by in situ XRD experiments leading to the knowledge of topological threshold in GeS 2–Ga 2S 3 glasses. The turning point of phase transformation behavior is demonstrated to be glasses containing 14–15 mol% Ga 2S 3. To interpret it a network demixing model is further improved and proposed for the structure of these ternary or quasi-binary chalcogenide glasses. For the nearest-neighbor coordination environment of glass with a transitional composition of 85.7 mol% (6/7) GeS 2·14.3 mol% (1/7) Ga 2S 3, six-coordinated [S 3Ga– X–GaS 3] units ( X= S or None) are well isolated by the [GeS 4] structures, which contributes to the decreasing of precipitation of Ga 2S 3 crystals in (100− x)GeS 2– xGa 2S 3 ( x≤14.3) glasses corresponding to the experimental evidence of the phase transformation behavior. This scenario of intermediate-range structural order, firstly, includes the arrangement of structural units which is consistent with and provides an atomistic explanation of the compositional evolution of phase transformation behavior in these glasses.