A sharp thermally reversing window in As45Te55−xIx chalcohalide glasses revealed by alternating differential scanning calorimetry and photo thermal deflection studies

The composition dependence of different thermal parameters such as glass transition temperature, non-reversing enthalpy, thermal diffusivity etc., of bulk As45Te55−xIx chalcohalide glasses (3 ⩽ x ⩽ 10), has been evaluated using the temperature modulated Alternating Differential Scanning Calorimetry (ADSC) and Photo Thermal Deflection (PTD) studies. It is found that there is not much variation in the glass transition temperature of As45Te55−xIx   glasses, even though there is a wide variation in the average coordination number (r¯). This observation has been understood on the basis that the variation in glass transition temperature of network glasses is dictated by the variation in average bond energy rather than r¯. Further, it is found that both the non-reversing enthalpy (ΔHnr) and the thermal diffusivity (α) exhibit a sharp minimum at a composition x = 6. A broad hump is also seen in glass transition and crystallization temperatures in the composition range 5 ⩽ x ⩽ 7. The results obtained clearly indicate a sharp thermally reversing window in As45Te55−xIx chalcohalide glasses around the composition x = 6.