Effects of chemical composition and mean coordination number on glass transitions in Ge–Sb–Se glasses

Abstract

Glass transitions in the Ge–Sb–Se glasses were investigated by means of differential scanning calorimetry (DSC) under non-isothermal conditions. The glass transition temperature [Formula: see text], activation energy of glass transition [Formula: see text], and fragility index as functions of the mean coordination number (MCN) and atomic percent of Ge were examined. The maximum value of [Formula: see text] in each group of the glasses occurred at the chemically stoichiometric composition, suggesting a glass transition threshold. The [Formula: see text] and fragility index were calculated from the heating rate dependence of [Formula: see text]. Both [Formula: see text] and fragility index show the minima at MCN = 2.4 which can be attributed to the structural phase transition of a covalently glassy network at MCN = 2.4. The analysis of the experimental results suggests that both the chemical composition and MCN have significant effects on the glass transitions in Ge–Sb–Se glasses.