Diffusion Phenomena of Silver Ion in Molten Sodium Borate by Chronopotentiometry

Diffusion phenomena of silver ion in the molten sodium diborate of low silver ion content were investigated at the temperature range from 880℃ to 625℃ by means of chronopotentiometry. From the results, it was shown that the silver ion was reduced reversibly to metallic state at the silver electrode used and silver ion was transported only by diffusion in case that transition time in a potential-time relation was within several seconds. Diffusion coefficients measured at various temperatures satisfied Arrhenius equation. The activation energy of diffusion and diffusion coefficient were respectively 32Kcal/mol and 6.5×10(-7) cm(2)/sec at the liquidous temperature. By comparing these values with those obtained in some molten salts, the difference of structure between the molten glass and molten salts was discussed. Moreover, the consideration for the size of borate anion existing in the molten glass was also tried from the viewpoint of rate process and from Stokes-Einstein's equation.