The tracer diffusivities of 22Na and 45Ca in 2 high-quality silica glasses were measured between 473 and 783K. The temperature dependences of the tracer diffusion coefficients in both glasses obeyed Arrhenius laws. The diffusion of 22Na was more than 6 orders of magnitude faster than the diffusion of 45Ca. The ionic conductivity was determined by using frequency-dependent impedance spectroscopy, and the conductivity diffusion coefficient, Dσ, was deduced from the direct-current conductivity via the Nernst–Einstein relationship. The temperature dependences of Dσ for both glasses also obeyed Arrhenius functions. The activation parameters and pre-exponential factors for tracer diffusion and for conductivity diffusion were determined. The activation enthalpy for 22Na, and the activation enthalpy for direct-current conductivity, were equal; thus showing that the conductivity of standard glasses was due to the motion of Na ions. The viscosity diffusivities were deduced from available viscosity data by using the Stokes–Einstein relationship. They were found to be considerably slower than both tracer diffusivities. The Haven ratio was temperature-independent for both glasses. The diffusivities of 22Na and 45Ca in soda-lime glasses increased with increasing Na2O content.

Diffusion of 22Na and 45Ca and Ionic Conduction in Two Standard Soda-Lime Glasses. E.M.T.Njiokep, H.Mehrer: Solid State Ionics, 2006, 177[33-34], 2839-44