Glass transition kinetics and optical band gap in Se85−xSb15Snx (x = 10, 11, 12.5, and 13) chalcogenide glasses

Se85−xSb15Snx (10 ≤ x ≤ 13) chalcogenide glasses were prepared by melt quenching technique. The glass transition temperature Tg of the samples was recorded at different heating rates using differential scanning calorimeter DSC. From the heating rate dependence of Tg, the activation energy for thermal relaxation Et was calculated using Moynihan model and Kissinger equation. It is found that Tg increases with Sn content due to enhancement of both the degree of cross-linking parameter Dcl and the mean bond energy of the average cross-linking per atom 〈Ecl〉. The observed increase in Dcl and 〈Ecl〉 is attributed to the formation of SnSe4/2 structural units of energies higher than that of Se–Se and Se–Sb bond energies. The decreasing trend of Et with the addition of Sn is an indication of improving thermal stability as it is also evident from the values of the temperature difference Tc − Tg. Correlation of Tg values with the physical parameters of the studied glasses (for instance, the average coordination number 〈Z〉, the average heat of atomization (Hs), the overall mean bond energy 〈E〉, and the optical band gap (Eg)) reveals that Tg increases linearly with 〈Z〉, Hs, and 〈E〉 but the behavior with Eg is opposite.