Thermally modulated differential scanning calorimetry of a glass of composition 45Na2O–40B2O3–10Al2O3–5In2O3

The kinetics of structural relaxation and of glass transition of the 45Na2O–40B2O3–10Al2O3–5In2O3 glassforming melt is studied by means of standard DSC and of temperature modulated DSC. In this way the dependence of the fictive temperature on cooling rate is determined simultaneously with the determination of the dependence of the dynamic glass transition temperature on modulation frequency. Both sets of data are fitted together in terms of the equation of Ritland–Bartenev. It was found that the activation energy of the structural relaxation exhibits a moderate dependence on temperature with the dimensionless fragility parameter α=3.3 (for strong systems, α is about 1 and increases to about 8 for some very fragile polymeric systems).