Silver ion exchange in glasses of the system Na2O/Al2O3/B2O3/SiO2

Glasses in the system Na2O/Al2O3/B2O3/SiO2 were studied with respect to their ionic conductivity and their silver/sodium interdiffusion coefficients. The densities and refractive indices as well as the optical transmission of the glasses before and after silver/sodium ion exchange were determined. Only trace quantities of silver occurred in the metallic state and the samples are widely transparent. With respect to the ionic conductivity, the glasses exhibit Arrhenian behavior. The specific ionic conductivities are correlated with the sliver interdiffusion coefficients. The gradient in the refractive index increases with increasing Na2O-concentration of the glass the gradient materials are prepared from, and decrease with increasing equimolar substitution of SiO2 by B2O3. Optimum glass compositions for the preparation of gradient index lenses possess B2O3-concentrations in the range of 12.5–15 mol% and molar Al2O3-concentrations few mol% larger than the respective Na2O-concentration.