Effects of oxides on optical absorption and homogeneity of GeS2-­Sb2S3-based glass

We investigated the effects of oxygen impurities on the optical absorption, glass structure, and homogeneity of a sulfide glass that is a potential candidate for use as an infrared-transmitting material. We prepared glasses based on the pseudo-binary GeS 2 -Sb 2 S 3 system by a conventional method using metals and sulfur as raw materials in an evacuated silica glass ampoule. The oxygen impurity content according to oxygen analysis was 0.034 mass% (340 ppm) for 20GeS 2 ·80SbS 3/2 glass. The oxygen impurities were distributed as oxides bonded to Ge and Sb with a distribution constant, although most of the oxygen was bonded to Ge. In addition, oxysulfide glasses were prepared by substituting GeO 2 or Sb 2 O 3 for the corresponding sulfides. In this case, the oxygen of the added oxides bonded mainly to Ge in the glasses. When more than 2 mol% of the oxides was substituted for the corresponding sulfides in the 20GeS 2 ·80SbS 3/2 glass, the glass became translucent or opaque. Microscopy observation revealed that droplet phases with diameters of 2 to 4 µm were precipitated. These phases were rich in germanium and oxygen. The inhomogeneity is induced by the addition of oxides to the glasses, particularly, in those with a large fraction of Sb 2 S 3 in the composition.