The diffusivity of Mg in monocrystalline Co1-xO samples was studied, at temperatures ranging from 1000 to 1600C and O partial pressures ranging from 10-8 to 0.21atm, by using microprobe analysis and secondary ion mass spectrometry methods. It was found that the results (table 48) could be described by the expression:

D (cm2/s) = 0.014 exp[-1.95(eV)/kT]

for an O partial pressure of 0.21atm and temperatures of between 1000 and 1600C, and by the expression:

D (cm2/s) = 0.004 exp[-2.07(eV)/kT]

for an O partial pressure of 10-5atm, and temperatures of between 1060 and 1455C. The dependence of the diffusivity upon the O partial pressure was of the form:

log [D (cm2/s)] = 0.0035[log(PO2)]2 + 0.22 log(PO2) - 8.4

at a temperature of 1200C and for pressures of between 10-8 and 0.21atm. It was concluded that the effect of the partial pressure upon Mg impurity diffusion was greater than that upon Co self-diffusion. This was attributed to a preferential attractive interaction between VCo" and Mg.

H.Boussetta, C.Monty: Journal of the Physics and Chemistry of Solids, 1988, 49[4], 369-75

Table 48

Diffusion of Mg in CoO