Study of correlations between glass-transition temperature and local structure of Ge-As-Se, Ge-As-Se-S chalcogenide glasses

The local structure and glass transition of Ge-As-Se, Ge-As-Se-Schalcogenide glasses have been studied by X-ray diffraction and differential scanning calorimetry. By applying the theory of topological constraints and considering chemically ordered network models, it has been determined that Ge10As20S10Se60 (average coordination number < r > = 2.4), Ge25As10S25Se40 (< r > = 2.6) are the compositions associated with the more stable glasses. This result is related to the larger differences between the glass transition (T-g) and crystallization-transition (T-cr) temperatures (Delta Tg-cr similar to 38 and 43 K) at these compositions. Relatively high values of short-range (d similar to 5.7-6.34 angstrom) and medium-range (L similar to 26.59-33.74 angstrom) order parameters of the local structure in the glass compositions satisfying the mentioned conditions affect the glass-transition temperature (T-g) and cause its value to increase (T-g similar to 589-689 K). As a result of comparative analyses of X-ray diffraction and differential scanning calorimetry curves it has been determined that there is a correlation between the glass-transition temperature (T-g) with the short range (d) and medium range order (L) parameters of the local structure.