Drift mobility and diffusion with an electric field of Ba2+ ions in NaCl crystals

Using a carrier-free tracer¹³³Ba the temperature dependences of the diffusion coefficientD and mobility of Ba²⁺ ions in an electric field have been measured on NaCl crystals in the temperature range from 500 to 750 °C. It is shown that the obtained values ofD are not affected by an electric field (30 V/cm) and that the temperature dependence of the mobility of Ba²⁺ ions is given by(T)=(12·3±1·9) exp [-(1·51±0·09) eV/kT]. Vacancy jump frequencies near a Ba²⁺ ion and the Gibbs free energy of association of this ion with a vacancy have been calculated in terms of a simple 5-frequency model for impurity diffusion by a vacancy mechanism.