Glass Transition and Fragility of Na₂O-TeO₂ Glasses
Glass transition and fragility of Na2O-TeO2 glasses
The heat capacity (Cp) change in the glass transition region for the xNa2O · (100−x)TeO2, mol%, glass forming melts with x=7.5, 11.1, 15.0, 20.0 and 25.0 was measured as a function of heating rate (2, 4, 6, 10 and 15 °C/min) using differential scanning calorimetry. The glass transition properties that have been measured and reported in this paper include the glass transition temperature (Tg), glass transition width (ΔTg), heat capacities in the glassy and liquid state (Cpg and Cpl) and the activation enthalpy for glass transition (ΔH*). Tg for these sodium tellurite melts decreased and ΔH* increased with increasing Na2O. Values of the ratio Cpl/Cpg ranged between 1.28 and 2.47, and the fragility parameter m (=ΔH*/RTg) ranged between 100 and 130, suggesting that these glass forming melts may be classified as intermediate between typical strong and fragile liquids. The viscosity, η, calculated at a few selected temperatures near the glass transition region decreased with increasing Na2O at any given temperature, which is also expected.
D. Zhu et al., "Glass Transition and Fragility of Na₂O-TeO₂ Glasses," Journal of Non-Crystalline Solids, Elsevier, May 2003.
The definitive version is available at http://dx.doi.org/10.1016/S0022-3093(02)01968-3
Materials Science and Engineering
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Article - Conference proceedings
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