Defect properties and diffusion in silver halides

Abstract

Recent results on the study of diffusion of several important cation and anion solutes in single-crystal AgBr and AgCl are discussed in the framework of defect properties established by earlier work which is briefly reviewed. The study of Ag⁺ diffusion in AgBr—AgI mixed crystals shows a monotonic increase in the diffusivity and a decrease in the activation enthalpy for diffusion with an increase in the iodide component. This may result from the decrease in the formation enthalpy for Frenkel defects with an increase in the elastic strain introduced by the oversized iodide ions. The surprisingly large enhancement of electrical conductivity and diffusivity of Ag⁺ in AgCl-Al₂O₃ composites is found to be due to the space charge effect and short-circuit diffusion at the grain boundary.