Self-diffusion was measured in single crystals of the -phase, at temperatures ranging from 1540 to 1697C, using 26Al as a radiotracer. It was found that 2 diffusion mechanisms were involved. These were a lattice diffusion mechanism and a sub-boundary mechanism, and the corresponding data could be described by:

D (cm2/s) = 0.16 exp[-510(kJ/mol)/RT]

and

D (cm2/s) = 1.3 x 1014 exp[-850(kJ/mol)/RT]

respectively. The results showed that the lattice diffusion coefficients of Al were much lower than those previously reported. A comparison with published O diffusion data for the same specimens showed that the O and Al diffusion coefficients were of the same order of magnitude in the lattice, but that the Al diffusion coefficients were greater than the O diffusion coefficients in sub-boundaries.

M.Le Gall, B.Lesage, J.Bernardini: Philosophical Magazine A, 1994, 70[5], 761-73

Table 4

Pipe Diffusion of Ag in Alumina