We show that changes in the relative mole fractions of Li2O and Na2O in alkali metaphosphate glasses lead to “anomalies” in the specific heat and structural relaxations. The heat capacity change between the liquid and glassy states, Δcp(Tg), at the calorimetric glass transition temperature, Tg, exhibits a minimum when the mole fractions of Li2O and Na2O are comparable. Moreover, systematic changes in the temperature dependence of the viscosity, η, i.e., changes in the “fragility” of the system, accompany these changes in mole fraction. This observed dependence of the “fragility” on the mixed alkali ion composition occurs in the absence of apparent changes in the covalent network connectivity which normally accounts for this behavior in glasses.
P. F. Green et al., "Specific Heat and Transport “Anomalies” in Mixed Alkali Glasses," Journal of Chemical Physics, vol. 109, no. 18, pp. 7907-7912, American Institute of Physics (AIP), Nov 1998.
The definitive version is available at https://doi.org/10.1063/1.477438
Materials Science and Engineering
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© 1998 American Institute of Physics (AIP), All rights reserved.
08 Nov 1998