J. Phys. IV France 07 (1997) C1-237-C1-238
Correlation Between the Reactivity Towards Oxygen and the Coercitivity in Submicron Vanadium Ferrite SpinelsV. Nivoix1, B. Gillot1, D. Aymes1, P. Perriat1, N. Millot1, S. Rousseau1 and M. Guyot2
1 Laboratoire de Recherche sur la Réactivité des Solides, UMR 5613, BP. 138, 21004 Dijon cedex, France
2 Laboratoire de Magnétisme et d'Optique de Versailles, 78035 Versailles, France
Nanometric powders of Fe2VO4 and Fe1.84V0.92Co0.23O4 have been synthetised by "chimie douce" process. The cations in the spinel structure can oxidize at low temperatures without any phase transformation leading to cationdeficient spinel with formula Fe2VO4+δ and Fe1.84V0.92Co0.23O4+δ, where δ is the deviation from stoichiometry, due to a change of the anion-cation ratio, consecutive to formation of vacancies. The oxidation, investigated by thermogravimetry, involves several stages, each stage corresponding to the oxidation of one oxidizable cation, Fe2+, V2+, V3+ on B (octahedral) or A (tetrahedral) sites. Coercivity has also been studied, revealing that the coercive field increases with the rate of oxidation.
© EDP Sciences 1997