Reaction kinetics and formation mechanism of magnesium ferrites

The reaction kinetics on the spinel formation reaction of Mg–ferrite formation during the heat-treatment of ferric and magnesium oxide powders has been evaluated by both Jander and Ginstling–Brounstein models. It revealed that the spinel formation could be successfully described by Janderʹs equation. The rate constant calculated by the Jander equation was 3 × 10−6 s−1 at 800 °C and increased to 1.4 × 10−3 s−1 as the reaction temperature increased up to 1000 °C. The activation energy of spinel formation was evaluated to be 335 kJ/mol, which was also confirmed by the differential thermal analysis. The activation energy coincided with that of Mg2+ diffusion reaction within MgO lattice suggesting this acted as a rate-determining step in the entire reaction.