OXYGEN SELF-DIFFUSION IN SUBBOUNDARIES OF ALUMINA SINGLE CRYSTALS

1 January 1990

journal article
Published by EDP Sciences in Le Journal de Physique Colloques

Vol. 51 (C1) , C1-1027
https://doi.org/10.1051/jphyscol:19901160

Abstract

Oxygen self-diffusion has been studied in alumina single crystals in the temperature range 1520-1750°C by means of the gas-solid isotope exchange technique. After diffusion annealing, profiles of oxygen-18 were determined by Secondary Ion Mass Spectrometry. Results indicate that two diffusion mechanisms are involved : a bulk diffusion mechanism and a subboundary one. The bulk diffusion mechanism can be described by: D(cm2/s) = 99.6 exp (- 626(kJ/mol)/RT) while subboundary coefficients obey: D' (cm2/s) = 3 x 1013 exp (-877(kJ/mol)/RT). The large value of the activation energy obtained for the subboundary diffusivity (larger than those related to the volume one) is attributed to the segregation of an impurity along the subboundaries

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