Heat Capacity and the Structure of Chalcogenide Glasses by Modulated Differential Scanning Calorimetry (MDSC)

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Abstract
The recent novel temperature-modulated differential scanning calorimetry (MDSC) technique has been applied to characterize the thermal properties of Te x Se100- x , As x Se100- x and Ge x Se100- x chalcogenide glasses in the glass transition region. All samples in this work were given the same thermal history. The reversing and non-reversing heat flows through the glass transformation region during both heating and cooling schedules were measured. The values of the relaxation enthalpy ΔH and heat capacity C p which characterize the thermal events in the glass transition region, were determined. The ΔH vs composition behavior shows a linear increase of ΔH with Te in Se100- x Te x glasses whereas for the Se100- x As x and Se100- x Ge x glasses ΔH evinces maxima at 16.6, 28.5, 40 at% As, and maxima at 20, 33, 40 at% Ge, respectively. The C p vs composition plot shows a linear decrease of C p with Te in Se100- x Te x glasses. In contrast, C p vs composition behavior for the Se100- x As x and Se100- x Ge x glasses, reveal minima at 16.6, 28.5, 40 at% As and maxima at 20, 33, 40 at% Ge respectively. We compare our MDSC results with previously published works on glass transition in these glasses and discuss the results in terms of recent structural models for chalcogenide glasses.