New method for preparation of specially pure glasses in the Ge–S–I system by melting the products of thermal decomposition of Ge2S3I2

Ge–S–I glasses having iodine content of 4.0–22.1 at.% and the x(S)/ x(Ge) ratio of 1.7–2.1 were prepared by melting and subsequent cooling of the products of thermal decomposition of Ge ₂S ₃I ₂. The maximum temperature of synthesis was 550 °С, and the homogenization duration of the glass-forming melt at 750 °С was 1 h. The compositions and properties of the resulting glasses and the impurity content in samples obtained under different conditions of Ge ₂S ₃I ₂ decomposition were investigated. The purest samples of prepared glasses were characterized by high optical transparency in the spectral range of 2–10 μm and the low content of impurities: silicon (0.1 ppm wt), metals (< 0.5 ppm wt) and hydrogen in the form of S–H bonds (0.02 ppm wt).