Volume diffusion of I- anions in near surface region of silver

Volume diffusion coefficients of I- anions in the near surface region of silver were determined using 131I. The distribution of the labelled ions with depth is determined by acid etching and counting the residual activity. The coefficient of diffusion is determined for surface layers of three different thicknesses over the temperature range 373-823 K. The mechanism proposed assumes the dissociation of Ag+I- in surface layer and the diffusion of I- into the interstitial free space immediately beneath the surface. This process is found to be accompanied by a small negative entropy change. (author) 8 refs.; 4 figs