Preparation and investigation of glasses in the GeS2–GeI4 system

• The GeS2–GeI4 glasses for fiber optics were prepared and investigated.
• For the first time, the crystallization of GeS2–GeI4 glasses has been studied.
• The stable glass macro-composition in the Ge–S–I system was determined.
• Transmission edges of GeS2–GeI4 glass samples were measured.

Glass samples of the GeS2–GeI4 system with iodine content of 5, 8, 10, 12 and 15 at.% are prepared by reacting germanium tetraiodide, germanium and sulfur in the evacuated silica–glass ampoules. The glass samples are characterized by high transparency in the spectral range of 0.55–10 μm. Regularities of changes in optical and thermal properties of the glasses depending on the iodine content are established. Transmission edges of samples are determined and impurity absorption bands are identified. The optimal iodine content in the Ge–S–I glasses for optical applications is determined to be equal to 10–12 at.%. Temperatures of glass transition, the onset of crystallization and starting of weight reduction of samples are determined. Chemical and phase compositions of the products of glass crystallization when heated up to 650 °C are investigated.