An-Najah Staff

The compactness of the structure of glassyGexBi6S94-x (14 ≤ x ≤ 26 at %) is determined from the measured densities. The peculiarities observed in the compactness-composition dependence are understood using Phillips’-Thorpe and Tanaka’s topological models proposed for the structure of these covalently bonded solids.

Differential scanning calorimetry measurements have been performed on elemental Se as well as on Ge_xSe_94−xIn₆ (x=4, 8, and 11 at%) and on Ge_ySe_88−yIn₁₂ (y=5, 7, and 9 at%) chalcogenide glasses. From the cooling rate dependence of the fictive temperature, the apparent activation energies, Δh*, and the fragility indices, m, as defined in the strong–fragile glass-forming liquid concept, are determined. It is found that, in Ge–Se–In system, there is an evolution from strong (m=67) to fragile (m=116) glass-forming liquids. The dependence of ‘m’ on the mean-coordination number, Z, is also obtained. This dependence is rationalized by assuming that, in this glassy alloy system, there is a tendency for the formation of In₂Se₃ clusters.