The diffusion of sulfur in nickel oxide single crystals was investigated at 1000 to 1250C. The measured data were found to deviate markedly from the erfc dependence for diffusion from a constant source. The diffusivities for the faster mode were given by:

D(cm2/s) = 2.94 exp[-86.6(kcal/mol)/RT]

while the slower mode gave,

D(cm2/s) = 1.08 x 10-9 exp[-32.8(kcal/mol)/RT]

W.Y.Howng, J.B.Wagner: Journal of Physics and Chemistry of Solids, 1978, 39[10], 1019-24