Molecular Struct’ure and Crystallization Behavior of Chalcogenide Glasses

Isothermal crystallization of ternary (Ge,S,), -X(Sn,S,), glasses is examined over the glass forming range 0 < x < 0.6. Time-temperature-transformation (TIT) curves are obtained using scanning calorimetry. The results show that both nucleation and growth processes dominate crystallization of the glasses in the range 0 < .Y < 0.25, but only growth processes are found to occur once x 2 0.25. The occurrence of this threshold composition correlates quantitatively with changes in glass molecular structure, recently probed by Raman scattering and Mossbauer spectroscopy.