The correlation factor for cobalt diffusion in NiO was determined via the simultaneous diffusion of 55Co and 60Co at 1179 to 1649C. The temperature dependence of the cobalt diffusivity in NiO in air was expressed by:

D(cm2/s) = 9.12 x 10-3 exp[-54160/RT]

W.K.Chen, N.L.Peterson: Journal of Physics and Chemistry of Solids, 1972, 33[4], 881-92