Se85-xSb15Snx (10 <= x <= 13) chalcogenide glasses were prepared by melt quenching technique. The glass transition temperature T-g of the samples was recorded at different heating rates using differential scanning calorimeter DSC. From the heating rate dependence of T-g, the activation energy for thermal relaxation E-t was calculated using Moynihan model and Kissinger equation. It is found that T-g increases with Sn content due to enhancement of both the degree of cross-linking parameter D-cl, and the mean bond energy of the average cross-linking per atom (E-cl). The observed increase in D-cl and (E-cl) 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 E-t with the addition of Sn is an indication of improving thermal stability as it is also evident from the values of the temperature difference T-c - T-g. Correlation of T-g values with the physical parameters of the studied glasses (for instance, the average coordination number (for the average heat of atomization (H-s), the overall mean bond energy (E), and the optical band gap (E-g)) reveals that T-g increases linearly with (Z), H-s, and (E) but the behavior with E-g is opposite. (C) 2011 Elsevier B.V. All rights reserved.