Enhancement of Lead Self-Diffusivity by Gold and Silver Additions

It has been proposed that noble-metal solutes diffuse in lead primarily by the interstitial mechanism, while cadmium solute diffuse by means of tightly bound interstitial-vacancy pairs. It is reasoned that noble-metal interstitial ions should also interact attractively with lead vacancies and result in a small enhancement of the self-diffusivity with solute additions. Consequently, lead self-diffusivity has been measured as a function of small gold- and silver-solute additions. The linear enhancement factors determined from these measurements are most consistent with the interpretation that noble-metal solutes diffuse primarily by the interstitial mechanism and that the relatively small enhancements of lead self-diffusion are due to attractively bound interstitial-vacancy pairs.