Thermal characterization of different compositions of Ge.sub.30-xSb.sub.xTe.sub.10Se.sub.60 (x = 0, 5, 10, 15, 20 at.%) glassy materials has been investigated through differential scanning calorimetry (DSC). The tested glasses have been synthesized by melt-quench technique. Glassy materials display compositional phase separation at x = 0, 5, 10, 15 at.%. For additional increase in Sb content at x = 20 at.%, the separation of phases combines in the glass matrix. The glass transition temperature (T.sub.g), initial temperature of crystallization (T.sub.c), peak crystallization temperature (T.sub.p) and melting temperature (T.sub.m) were found to be affected by both heating rate and composition. It is noticed that the increasing of antimony mass percentage in the glassy matrix is leading to decrease in T.sub.g, T.sub.c, T.sub.p and T.sub.m values. The melting temperature (T.sub.m) of these glasses was found in the range 733-746 K for the first phase and in the range 740-792 K for the second phase. The activation energy of glass transition (E.sub.g), activation energy for crystallization (E.sub.c), Avrami index (n) and fragility index (F.sub.i) were calculated using these specific temperatures. E.sub.g decreases with increasing Sb content in all studied samples, but E.sub.g is increasing in the sample with Sb content of 20%, and hence, it varies between 102.7 and 110.6 kJ approximately, whereas (E.sub.c) decreases with the increase in the Sb content in all the tested samples and varies between 283 and 339 kJ. The fragility index varies between 10 and 26 indicating that the melts of these glasses are strong, and the fragility is minimum. The results were discussed in terms of the average coordination number N.sub.C and chemical bond approach.