CREEP AND OXYGEN DIFFUSION IN MAGNETITE

The creep rate of polycrystalline Fe3O4 has been measured as a function of stress and oxygen partial pressure in the temperature range 480-1100-degrees-C. A regime of power law creep is found at high stress, with a stress exponent of congruent-to-3.1 and an activation energy of 264 kJ/mol. A regime of diffusional flow is found at lower stresses and is interpreted as Nabarro-Herring creep. The data for the two regimes are combined to deduce an oxygen diffusion coefficient of confruent-to-10(-5) exp(-264kJ/mol/RT)m2s-1, with oxygen vacancies suggested as the mobile species.