Samples of polycrystalline material were studied at temperatures of between 750 and 1050C by using a groove and stain technique. It was shown that the Fisher model for grain boundary diffusion accurately described the data when an infinite source was assumed. It was found that the bulk diffusion data were described by:

D(cm2/s) = 1.6 x 1015 exp[-2.09(eV)/kT]

while the grain boundary diffusivity was described by:

D(cm2/s) = 4.0 x 10-5 exp[-1.4(eV)/kT]

A grain boundary width of 0.5nm was assumed in the latter case.

P.H.Holloway, T.Abrantes: Journal of Vacuum Science and Technology A, 1989, 7[3], 1573-8