Ion exchange properties of and rates of ionic diffusion in beta-alumina

The sodium ion in beta-alumina has been exchanged in molten salts with a number of univalent and divalent ions. The sodium and potassium concentrations in the solid beta-alumina in contact with various binary NaK nitrate compositions have been carefully determined and the free energy difference between K+ and Na+ beta-alumina calculated. The self diffusion coefficients of Na+, Ag+, K+, Rb+, and Li+ in single crystals of beta-alumina have been determined as a function of temperature. Sodium ion has the largest self diffusion coefficient (1 × 10−5 cm2/sec at 300°C and 4·0 × 10−7 cm2/sec at 25°C) followed by Ag+. L+, Li+, and Rb+. Data are also presented for interdiffusion conefficients and dielectric loss measurements, and some speculations are made as to the mechanism of the diffusion.