AVERAGE COORDINATION-NUMBER DEPENDENCE OF GLASS-TRANSITION TEMPERATURE IN GE-IN-SE CHALCOGENIDE GLASSES

Twenty-six glassy compositions, belonging to the GexIn6Se94-x and GexIn12Se88-x families of the Ge-In-Se system, were prepared from high purity constituent elements. Differential Scanning Calorimetry (DSC) measurements were carried out on these glasses. The DSC thermograms were used to determine the glass transition temperatures (T-g) for the compositions examined. The T-g-composition dependence of the GexIn6Se94-x family shows a minimum in T-g at a value of the average coordination number, [r], equal to 2.4. For both families of the glasses examined, the T-g-[r] dependence displays maxima at [r] = 2.75 and [r] = 2.83 for GexIn6Se94-x and GexIn12Se88-x families, respectively. These results are interpreted by using the Phillips model of rigidity percolation and Chemically Ordered Covalent Network (COCN) model.