Self-diffusion was measured under an O partial pressure of 10-4atm (table 69). The samples were annealed in an Ar flow containing 100ppm of 18O. The diffusion profiles were obtained by means of secondary ion mass spectrometry, and were consistent with solutions of Fick’s laws which included the effect of evaporation/condensation at the surface of the sample. The measurements showed that, near to 1300C, the dependence upon PO2 was very small. On the other hand, the change in the pre-exponential with PO2 was significant at 1555C. this led to a small effective activation energy below 10-4atm. This behaviour could be explained by assuming that, as well as 2 different charge states of the majority defects, they were 2 types of minority defect in the O sub-lattice: O vacancies and O interstitials.

Influence of Oxygen Pressure on Oxygen Self-Diffusion in NiO. C.Dubois, C.Monty, J.Philibert: Solid State Ionics, 1984, 12, 75-8

Table 69

Diffusion of O in NiO at PO2 = 0.0001atm