Heterophase inclusions and dissolved impurities in Ge25Sb10S65 glass

The impurity content and microhomogeneity of Ge25Sb10S65 glass samples, prepared by direct synthesis from elements, were investigated. It was shown that the increase in temperature of synthesis of the glass-forming melt resulted in the increase of the content of impurities of H, Na, Al, Si, K, Ca and transition metals in the prepared glasses. The glasses from the melt, subjected to chemical-distillation purification, were characterized by the low content of gas-forming impurities and the increased content of Al, Si and Cl. The glasses contained heterophase impurity inclusions mainly consisting of SiO2, and their concentration and size depended on the conditions of glass preparation. The impurity content in the purest glasses was as follows: oxygen - <0.5 ppm wt, carbon - <5 ppm wt, hydrogen - 0.1 ppm wt, Si - <1 ppm wt, transition metals - <0.25 ppm wt, heterophase impurity inclusions with sizes larger than 80 nm - <102 cm3. It was shown that heterophase impurity inclusions behaved as the centers of glass crystallization.