Diffusion of Gold and Silver in Tin Single Crystals

Abstract

The diffusivities D of gold and silver in high-purity tin have been measured along the ``c'' and ``a'' directions in the temperature range 135°–225°C. They are described by DAu/Snc = 5.8×10−3 exp−(11 000/RT) cm2sec−1, DAu/Sna = 1.6×10−1 exp−(17 700/RT) cm2 sec−1, DAg/Snc = 7.1×10−3 exp−(12 300/RT) cm2 sec−1, and DAg/Sna = 1.8×10−1 exp−(18 400/RT) cm2 sec−1. These results are characterized by a very large anisotropy of diffusion compared with that found for the self-diffusion of tin. Furthermore, these solutes diffuse orders of magnitude faster than the self-diffusion of tin and also they diffuse fastest along the ``c'' direction, whereas tin diffuses fastest along the ``a'' direction. This unusual behavior is interpreted as evidence that silver and gold dissolve interstitially in tin and diffuse by an interstitial mechanism.