Diffusion Phenomena in Nonstoichiometric Copper Sulfide and Selenide.

From graphs of the decrease in the concentration polarization and from coulometric titration curves the values of the coefficient of combined chemical diffusion of cations and electrons and of the coefficient of self-diffusion of copper in the mixed ionic-electronic conductors Cu//2// minus // delta X (X equals S//1Se) are calculated for various values of delta at 670 K. The coefficient of combined diffusion decreases with an increase in delta , while the coefficient of self-diffusion does not depend on the degree of nonstoichiometry of the samples. The experimental and theoretical dependences of the coefficient of combined diffusion in Cu//2// minus // delta X on delta are in satisfactory agreement with each other.