Tracer diffusion coefficients of the radioactive 22Na isotope were measured in glasses of the type, (CaO,Al2O3)x(2SiO2)1−x in order to study the diffusion of Na as a function of glass composition, temperature and initial water content. The diffusion of 22Na in glasses which were annealed in dry air could always be well-described by a single tracer diffusion coefficient, but sometimes not in samples annealed in common air. It was found that the Na tracer diffusion coefficient decreased by about 6 orders of magnitude when the glass composition, x, changed from 0 to 0.75 at 800C. The temperature dependence of the Na diffusion seemed to decrease as the silica content increased. Variations in the initial water content of some of the glasses did not significantly influence the rate of Na tracer diffusion.

Sodium Tracer Diffusion in Glasses of the Type (CaO·Al2O3)x(2SiO2)1−x. H.Lu, R.Dieckmann: Journal of Non-Crystalline Solids, 2007, 353[26], 2528-44