J. Phys. Colloques
Volume 51, Numéro C1, Janvier 1990Proceeding of the International Congress
Intergranular and Interphase Boundaries in materials
|Page(s)||C1-1027 - C1-1033|
OXYGEN SELF-DIFFUSION IN SUBBOUNDARIES OF ALUMINA SINGLE CRYSTALSD. PROT, M. MILOCHE et C. MONTY
C.N.R.S., Laboratoire de Physique des Matériaux, 1, Place A. Briand, Bellevue, F-92195 Meudon Cedex, France
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.