Influence of gallium and alkali halide addition on the optical and thermo-mechanical properties of GeSe2-Ga2Se3 glass

A systematic compositional study of a new family of chalcogenide glasses, transparent from the visible range up to 16 mu m has been performed. Numerous glass forming regions were explored in the GeSe2-Ga2Se3-MX system (MX = alkali halide) in order to understand the role of alkali halides and the effect of Ga substitution for Sb in the glass structure. To that avail, several ternary diagrams were investigated, and optical and thermo-mechanical measurements were performed. It is shown that the introduction of an alkali halide in the GeSe2-Ga2Se3 glasses increased the band-gap energy E-g by stabilizing electrons from the lone pairs of selenium. However, the glass hardness was lowered due to a decrease in the glass network reticulation. The chemical resistance was studied in a glass containing high CsCl content. Significant corrosion occurred when the glass was exposed to hot water for several hours. There is a great deal of interest in these glasses for use in thermal imaging devices, as they permit the alignment of infrared optical systems with visible red light. Furthermore, the low cost of raw materials and the possibility of shaping these glasses into lenses by molding could extend their utilization from defense to civilian applications.