ガラス中における一価カチオンの拡散プロフィルに関する一考察  [in Japanese] Some Considerations on the Diffusion Profile of Monovalent Cations in Glass  [in Japanese]

Diffusion data of monovalent cations in glass have been analysed on the basis of several theoretical equations. Main results are as follows : 1. It was predicted that the following characteristics were applicable to the inter-diffusion data; (1) time-dependence of the depth of diffusion, (2) comparison of the diffusion profile with standard profiles derived by Fujita, and (3) linear relationship between the reciprocal of the inter-diffusion coefficient and the ion concentration. Many of the present data were, however, found not to satisfy the linearity (3). 2. Self-diffusion coefficient of Na^+, D_<Na>^*, derived from extrapolation of the curve (3), differs largely from the one, measured with isotope ^<24>Na. It is attributed to the difference of the field of diffusion in both cases, i.e., the D_<Na>^* itself is a function of concentration. Temperature-dependence of D_<Na>^* is larger than expected. 3. Partition coefficient of monovalent cation between the molten salt and the glass varies largely depending on the cation species. However, linear relationship is held between the reciprocals of the equilibrium concentrations of the distributed ion in both phases. Activity coefficients of the ions in glass can be approximately calculated from these equilibrium data and heat of mixing of molten salts in literatures. 4. Although the linearity (3) is somewhat improved by introducing these coefficients, the discrepancy is still large. The variations of ratio D_<Na>^*/D_M^* (M=K, Ag) are discussed on the basis of the irreversibility of the diffusion processes.