Diffusion of Sodium in Rubidium Chloride

The diffusion of ${\mathrm{Na}}^{22}$Cl in RbCl was measured in the temperature range 377-707°C by the tracer-sectioning technique. The activation energy is 2.06±0.02 and 0.59±0.01 eV in the intrinsic and extrinsic regions, respectively. The temperature dependence of the correlation factor, as deduced from isotope-effect measurements, is 0.19 eV in the intrinsic region and -0.05 eV in the extrinsic region. When a theoretical value for the ${\mathrm{Na}}^{+}$-vacancy binding energy is used, values of $\frac{1}{2}{h}_f=1.22\mathrm{}$ eV and $h_m=0.55\mathrm{}$ eV are obtained, where $h_f$ is the energy of formation, and $h_m$ the energy of motion, of a cation vacancy. These values are not in agreement with the calculation by Tosi and Doyama.