Analysis of thermophysical properties of lead silicates in comparison to bulk metallic glasses

Abstract

The equilibrium viscosity and the specific heat capacity of three lead silicate glass forming liquids (flint glasses) with low glass transition temperatures are experimentally measured and compared to the thermophysical properties of network glass-formers like SiO2 and GeO2 and of bulk metallic glasses. The data are analyzed using the Vogel–Fulcher–Tammann (VFT) equation, the Mauro–Yue–Ellison–Gupta–Allan (MYEGA) equation, and the Adam–Gibbs approach. The flint glasses depart from the Arrhenius equation in terms of liquid kinetics and their corresponding kinetic fragilities are intermediate between GeO2 and the bulk metallic glass-formers. Among the lead silicates the fragility increases with increasing content of network modifiers, as lead, sodium and potassium modify the silicate network by creating non-bridging oxygen that softens the network.