The electrical conductivity of crystalline sodium chloride. (Defect interactions)

The electrical conductivity of NaCl and NaCl+SrCl 2 was measured over a wide temperature range and fitted by a least squares method to the conventional Schottky defect model which allows for specific nearest neighbour defect interactions and Coulomb interactions treated in the Debye-Huckel approximation, at greater separations. Doped crystals showed small systematic deviations between theory and experiment and gave abnormally high enthalpies and entropies of association between cation vacancies and impurities. Defect formation and migration parameters are quoted. They predict single vacancy diffusion coefficients in moderate agreement with experiment although the predicted anion activated energy appears to be definitely too large.