Concentration Dependence of the Interdiffusion Coefficients in Molten Alkali Nitrate — Silver Nitrate Mixtures

Abstract

Abstract To measure the composition dependence of the interdiffusion coefficients in molten mixtures of alkali nitrates and silver nitrate, a wave-front-shearing interferometer, together with an initial “plane source” was used. With this technique, the diffusion coefficients were measured in nearly differential steps in the three mixtures (Na,Ag)NO3 , (K,Ag)NO3 , and (Rb,Ag)NO3 at 300°C. The composition dependence of the diffusion coefficients D of all three systems could be described by parabolas of the form D = a + b x 2 + c x2 2, where x2 denotes the mole fraction of the silver nitrate. The three coefficients a,b, and c all show a clear proportionality to the radii of the akali ions. Thus an extrapolation to the not measured systems (Li, Ag)NO3 and (Cs, Ag)NO3 was possible.