Thermal characterization of (As2Se3)0.5(As2Te3)0.5 infrared glass

The structural relaxation and crystallization kinetics of the (As2Se3)0.5(As2Te3)0.5 chalcogenide glass was studied by means of differential scanning calorimetry (DSC) and the influence of experimental conditions (particle size, heating rate) was observed. The Tool-Narayanaswamy-Moynihan (TNM) model was used for description of structural relaxation data. The structure of the studied glass was found to be similar to its purely selenide analogue (As2Se3), but the Te atoms appear to randomly incorporate into the short Se-As-Te chains; also they coexist in AsTe3/2 pyramidal units alongside the AsSe3/2 units. In case of the description of the crystallization kinetics, the nucleation-growth Johnson-Mehl-Avrami (JMA) model and the semi-empirical autocatalytic AC(M,N) model were tested on experimental DSC data. The suitability of JMA model was not confirmed due to the complexity of crystallization, therefore the AC(M,N) model was applied. These results were supported by the structural information from XRD analysis, Raman spectroscopy and infrared (IR) microscopy. The presence of As-Te, As-Se and As2Se(Te)3 phases was confirmed and the occurrence of tellurium in the structure has a huge influence on overall structure and subsequent thermal behavior of the (As2Se3)0.5(As2Te3)0.5 glassy material.