Diffusivities of polyvalent elements in a 15Na2O · 85SiO2 glass melt

Abstract Diffusivities of various polyvalent elements (Sn 2+ , As 3+ , As 5+ , Sb 3+ , Sb 5+ , Ti 4+ , V 4+ , V 5+ , Cr 3+ , Fe 3+ and Cu + ) were measured in a melt with the basic composition of 15Na 2 O · 85SiO 2 . The method used was the square-wave voltammetry. Within the temperature range of 1300–1550°C, a linear correlation between log D and 1/ T was observed. At lower temperatures, diffusion coefficients were larger than expected from an Arrhenius temperature dependence. This effect is explained by the crystallization of cristobalite below 1300°C. Under this condition, the residual melt is enriched in Na 2 O and the decreasing viscosity leads to higher diffusivity. The results are compared with those obtained from a silicate melt richer in soda content.