Interstitial Diffusion of Gold and Silver in Indium

Abstract

The diffusivities $D$ of silver in the $c$ and $a$ directions of indium and gold in randomly oriented single crystals of indium have been measured by a radioactive-tracer technique. They are described by: ${{D}_{\frac{\mathrm{Ag}}{\mathrm{In}}}}^{\mathrm{a}}=5.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}1} \mathrm{exp}(\ensuremath{-}\frac{12800}{\mathrm{RT}})$, ${{D}_{\frac{\mathrm{Ag}}{\mathrm{In}}}}^{\mathrm{c}}=1.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}1} \mathrm{exp}(\ensuremath{-}\frac{11500}{\mathrm{RT}})$, and ${D}_{\frac{\mathrm{Au}}{\mathrm{In}}}=9\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3} \mathrm{exp}(\ensuremath{-}\frac{6700}{\mathrm{RT}})$. The rates of diffusion of silver and gold in indium are thus several orders of magnitude greater than the self-diffusion rate of indium. These results indicate that gold and silver are dissolved at least partly in the interstitial state, in agreement with a theory which predicts that $d\ensuremath{-}d$ correlation forces should cause dissolved noble metals to favor interstitial sites in indium.