THE TG VERSUS Z DEPENDENCE OF GLASSES OF THE GE-IN-SE SYSTEM

The results of measurements on the variation of the glass transition temperature (T(g)) with the average coordination number (Z) are reported and discussed for glasses Of the Ge-In-Se system. The study covers families of compositions with 5 and 8 at.% In, as well as compositions along the GeSe2-In2Se3 tie line. In the T(g)-Z data of these glasses, a change in slope is seen at Z congruent-to 2.40. In addition, maxima in T(g) are observed at Z values corresponding to the tie line compositions of the system. An account of these features is given by the existing Phillips model and the chemically ordered network model. Some of the features observed can be explained by the formation of specific structural units in these glasses. The explanations corroborate our conclusion that, in addition to the features which have a topological origin, effects due to local chemical ordering are also observed in the glasses of this system.