A Comparative Study of Purification Routes for As2Se3 Chalcogenide Glass

Chalcogenide glasses have been widely studied due to their extraordinary transparency in the mid-infrared region. Their transparency, combined with tailorable thermo-mechanical properties, makes them ideal candidates for various optic applications. Extrinsic impurities within the glass matrix can impede their integration in components where low optical loss is a requirement. Additionally, chalcogenide materials typically exhibit low mechanical strength due to the comparatively weaker average bond strength of constituents. Here, we report findings of efforts to explore various purification methods on As2Se3 glasses to improve their optical and mechanical properties. These methods involve oxides removal by thermal treatment of the reagents, and addition of AlCl3 impurity-getters in the melt followed by distillation. We show that these techniques yield very effective results on the removal of hydroxyls, water, and oxide impurities. We also observe a recurrent increase in the Se-H vibrational band, with the concentration of the Se-H species escalating to several tens-of-ppm, depending on the purification method. These increases are associated with the preferential dissociation of hydrogen-containing species. Investigations of the structural, thermal, and mechanical properties of the glass were compared as a function of purification method, and the influence of impurity content on these material attributes is presented.