Abstract
The diffusion coefficients of oxygen in single crystals of nickel ferrite with Fe/Ni=3.4 were determined as a function of oxygen stoichiometry between 1140° and 1340°C. The diffusion kinetics were followed by measuring the rate of exchange of 18O between the gas and solid slabs of ferrite, and the oxygen stoichiometry was established by controlling total pressure of oxygen in the gas phase. At higher oxygen contents, the diffusion coefficient is independent of stoichiometry and is given by D=10‐2.3exp cm2/s. At low oxygen contents the diffusion rate depends strongly on oxygen stoichiometry and is smaller. In polycrystalline ferrite the diffusion at 1197°C is 40 times faster than in single crystals but shows the same dependence on oxygen stoichiometry. Probable diffusion mechanisms are discussed.
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