The diffusion of 63Ni along grain boundaries in the pure oxide was studied under a pressure of 1atm at 500 to 600C, or under a pressure of 7 x 10-6atm at 700C. Under the former conditions, the results could be described by:

Dδ (cm3/s) = 3.0 x 10-8 exp[-1.78(eV)/kT]

The width of the boundary was assumed to be equal to 7 x 10-8cm.

A.Atkinson, R.I.Taylor: Philosophical Magazine A, 1981, 43[4], 979-98