Silver and platinum diffusion in alumina single crystals

Silver and platinum diffusion in oc-alumina single crystals have been inves tigated using SIMS technique in 800-1150 degreesC and 900-1200 degreesC tem perature ranges. Previous radiotracer measurements yielded higher diffusion coefficients of silver than those presented here. This difference is attri buted to the resolution differences between the SIMS and the radiotracer te chniques. The former allows us to obtain the bulk diffusion coefficients wh ile the latter the dislocation ones. Silver and platinum diffusion coeffici ents are one to two orders of magnitude higher than those of chromium and a luminium. It is suggested that such a difference can be related to the abil ity of low valency cations to occupy interstitial sites, allowing a proport ion of the noble elements to dissolve in alumina through the self-compensat ing mode. Hence, a diffusion mechanism involving correlated jumps of inters titial and substitutional foreign atoms (Ag, Pt) is proposed. (C) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All righrs reseved.