Silver and platinum diffusion in alumina single crystals

Silver and platinum diffusion in oc-alumina single crystals have been investigated using SIMS technique in 800-1150 degreesC and 900-1200 degreesC temperature ranges. Previous radiotracer measurements yielded higher diffusion coefficients of silver than those presented here. This difference is attributed to the resolution differences between the SIMS and the radiotracer techniques. The former allows us to obtain the bulk diffusion coefficients while the latter the dislocation ones. Silver and platinum diffusion coefficients are one to two orders of magnitude higher than those of chromium and aluminium. It is suggested that such a difference can be related to the ability of low valency cations to occupy interstitial sites, allowing a proportion of the noble elements to dissolve in alumina through the self-compensating mode. Hence, a diffusion mechanism involving correlated jumps of interstitial and substitutional foreign atoms (Ag, Pt) is proposed. (C) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All righrs reseved.