Diffusion of Sodium in Rubidium Chloride

Abstract

The diffusion of ${\mathrm{Na}}^{22}$Cl in RbCl was measured in the temperature range 377-707\ifmmode^\circ\else\textdegree\fi{}C by the tracer-sectioning technique. The activation energy is 2.06\ifmmode\pm\else\textpm\fi{}0.02 and 0.59\ifmmode\pm\else\textpm\fi{}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 $\frac{1}{2}{h}_{f}=1.22$ eV and ${h}_{m}=0.55$ 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.