Oxygen Mobility in Polycrystalline NiCr2O4 and α-Fe2O3

Oxygen diffusion coefficients have been determined for polycrystalline samples of NiCr₂O₄ and α-Fe₂O₃ by exchange measurements with oxygen gas containing the stable isotope¹⁸O, using mass spectrometer analysis. Oxygen diffusion in NiCr₂O₄ can be represented by the equation D = 0.017 exp (-65,400/RT); oxygen diffusion in α-Fe₂O₃ can be represented by the equation D = 1 × 10¹¹ exp (-146,000/RT). The large difference between D₀ and activation energy for these materials suggests that different diffusion mechanisms are involved.