Self-Diffusion, Conductivity and Transport Numbers in Alkali Halide Single Crystals

Abstract

The self-diffusion coefficients of the anions and cations have been measured in pure and doped NaCl and KCl crystals, together with the ionic conductivity. The experimental results give evidence for migration mechanisms via free cation and anion vacancies and vacancy pairs. Analysis of the complete set of diffusion data leads to the determination of the entropy and enthalpy of formation and migration of these defects. In a second part, the diffusion coefficients via free vacancies are compared with the conductivity data in order to investigate the validity of the Nernst-Einstein relation. This relation is found to be verified within 2%, in NaCl as well as in KCl, no appreciable correlation effect being detected.