Oxygen Self-Diffusion in Y sub 2 O sub 3 Doped alpha Alumina

Oxygen self-diffusion have been measured in single and polycrystals of alpha Al sub 2 O sub 3 doped with Y sub 2 O sub 3 in the temperature range 1110-1630 C, with exp 18 O sub 2 and SIMS. On monocrystals, two mechanisms are involved: a bulk diffusion mechanism and a sub-boundary one. At high temperature these two mechanisms are observed when at lower temperature bulk mechanism predominates. Lattice and sub-boundary diffusion coefficients obey respectively the equation: D sub l (cm exp 2 /s)=67 exp[-590 (kJ.mol exp -1 )/RT] and Dsb (cm exp 2 /s)= 10 exp 17 exp[-977 (kJ.mol exp -1 )/RT]. In polycrystals, grain boundary diffusion is given by: Dgb(cm exp 2 /s)= 5.10 exp 11 exp[-835(kJ.mol exp -1 )/RT]. Comparing with results obtained in undoped alpha Al sub 2 O sub 3 , it appears that Y slightly increases oxygen bulk diffusion and decreases grain boundary diffusion.