The diffusion of cadmium ions in solid potassium chloride

Abstract

The diffusion o fCd ++ ions in KC1 crystals has been studied over the temperature range of 350–500°C by diffusing from radioactively tagged CdCl 2 vapor. It was found that the diffusion coefficients of Cd could be expressed as functions of impurity concentration by means of the Lidiard equation for diffusion by impurity-vacancy complexes. The diffusion of the impurity-vacancy complexes as a function of temperature is given by: D 0(Cd) = 4.68 × 10 −5 exp( −12, 400 RT ) cm 2 sec . The free energy of association was fairly constant from 378 to 505°C and had an average value of 0.51 eV. These values are compared with those for other complexes and with theoretically cal- culated values. As in previous work on diffusion of Pb 2+, an anomalously high rate of diffusion was observed near the surface in some experiments.