Samples of polycrystalline material were studied at 750 to 1050C by using a groove and stain technique. It was found that the bulk diffusion data were described by:
D (cm2/s) = 4.0 x 10-5 exp[-1.4(eV)/kT]
P.H.Holloway, T.Abrantes: Journal of Vacuum Science and Technology A, 1989, 7[3], 1573-8