Contamination of glassy arsenic sulfide by SiO2 particles during melt solidification in silica glassware

Abstract It is found that the content of SiO 2 inclusions in the As 2 S 3 volume is increased during chalcogenide glass melting in silica glassware with subsequent cooling to solid sample and separation from the container walls. The experiment consisted in repetition of cycles of “chalcogenide ingot melting and heating to 450–600 °C - cooling the melt to a glass transition temperature - separation of the sample from the silica-glass container walls - cooling to room temperature”. Content and size of the inclusions in the initial glass and the samples after the “melting–solidification” cycles was controlled by means of laser ultramicroscopy and optical microscopy. The concentration of micrometer-sized particles was found to increase with cycles of melting and solidification. The increase of particles concentration is explained by the combined effect of a number of factors such as high adhesion of glassy arsenic sulfide to silica glass and strong radial and longitudinal shrinkage of the chalcogenide ingot during cooling compared with silica-glass container due to significant differences in their linear coefficients of thermal expansion. It leads to destruction of the adhesion contact along the boundary of solid phases and the surface layers of glasses with separation of microprotrusions and fragments of silica glass surface and their fixation in the surface layers of As 2 S 3 glass. The excess optical losses in glassy arsenic sulfide, caused by this type of contaminating action of apparatus, have been estimated.