Viscosity and Its Temperature Dependence in Molten BeF2

Abstract

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.