Viscosity and Its Temperature Dependence in Molten BeF2

The viscosity of molten beryllium fluoride has been measured with coaxial-cylinder viscometers over five orders of magnitude (limits: 979°C, 28.6 P; 574°C, 2.24 × 106 P). Over the experimental range of shear stresses, BeF2 behaves as a Newtonian fluid. Like SiO2, its high-temperature analog, BeF2 shows an Arrhenius temperature dependence over several orders of magnitude in viscosity. Reported heat-capacity data for BeF2 and SiO2 and the Adam-Gibbs theory indicate that the Arrhenius viscosity behavior of these liquids may be explained in terms of the configurational entropy which is virtually constant at temperatures above the glass-transition temperature.