THERMAL-EXPANSION AND NETWORK CONSTRAINTS IN GE-IN-SE GLASSES

The linear thermal expansion coefficient, alpha, as a function of temperature is reported and discussed for Ge-In-Se glasses. The study covered glasses with 5 and 8 at.% In and glasses across the GeSe2-In2Se3 tie line. Changes in slope of the alpha vs. the average coordination number, Z, are seen at Z values of congruent-to 2.40 and = 2.67. The alpha-temperature data of glasses with Z up to 2.40 are different from those with Z values between = 2.40 to = 2.67. Changes in slope are seen at Z values of congruent-to 2.40 and congruent-to 2.67 in the softening temperature, T(s), vs. Z data. Peaks in T(s) are seen at Z values corresponding to tie line compositions of the families with In at 5 and 8 at.% which have Z values of 2.73 and 2.77, respectively. These results confirm the earlier conclusion that, in addition to features arising due to effects of topology, those due to local chemical ordering are also present.