Structure and physicochemical properties of glasses in the (As₂Se₃)_{1 − z} -(SnSe₂) _{z − x} -(Tl₂Se) _x and (As₂Se₃)_{1 − z} -(SnSe) _{z − x} -(Tl₂Se) _x systems

Abstract

A comparative investigation of glasses in the As₂Se₃)_{1 − z} -(SnSe₂) _{z − x} -(Tl₂Se) _x and (As₂Se₃)_{1 − z} -(SnSe) _{z − x} -(Tl₂Se) _x systems has been performed. In both systems, the glass formation regions are shifted toward the As₂Se₃ compound. Only tin(IV) in the structure of glasses in the (As₂Se₃)_{1 − z} -(SnSe) _{z − x} -(Tl₂Se) _x system is identified by Mössbauer spectroscopy, whereas glasses in the (As₂Se₃)_{1 − z} -(SnSe) _{z − x} -(Tl₂Se) _x system contain both Sn(II) and Sn(IV). The presence of tin in the oxidation state 2+ in the structural network of the glasses does not lead to impurity conduction. The dependences of the density, the microhardness, and the glass transition temperature on the glass composition are explained in the framework of the model according to which the structure of these glasses is built up of structural units corresponding to the As₂Se₃, AsSe, TlAsSe₂, Tl₂Se, SnSe, and SnSe₂ compounds. It is established that, for crystalline alloys in the (As₂Se₃)_{1 − z} -(SnSe) _{z − x} -(Tl₂Se) _x system, there exist two compounds (Tl₂SnSe₃ and Tl₄SnSe₄), which are formed by the peritectic reactions; however, structural units of these compounds are not formed in the structural network of glasses.