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 Jander's 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.