The diffusion of 51Cr in polycrystalline NiO was studied at 600 to 1100C, under O at a pressure of 1atm. The lattice solubility of Cr was not negligible, and Cr also segregated strongly to NiO grain boundaries. A procedure for analysing the penetration profiles of such an impurity was developed in which the parameters describing segregation and grain boundary diffusion were deduced self-consistently:

D (cm2/s) = 6.5 x 10-3 exp[-2.0(eV)/kT]

When combined with previous measurements of Ni and Co diffusion, it was found that grain-boundary coefficients decreased in the order: Co, Ni, Cr, Ce; as was also found for lattice diffusion (except for Ce, with its negligible bulk solubility).

Impurity Diffusion in NiO Grain Boundaries. A.Atkinson, R.I.Taylor: Journal of Physics and Chemistry of Solids, 1986, 47[3], 315-23