CATIONIC DISTRIBUTION AND OXIDATION-KINETICS OF DIVALENT MANGANESE IONS IN IRON MANGANITE SPINELS MN3-XFEXO4 (0-LESS-THAN-X-LESS-THAN-1.50)

A quantitative analysis by derivative thermogravimetry based on the di fference of reactivity in oxygen of Mn2+ ions of iron manganite spinel s Mn3-xFexO4 with 0 < x < 1.50 in relation to the occupied site (octah edral B site or tetrahedral A site) permits a cation distribution to b e proposed. Kinetics studies on the oxidation process of Mn2+ ions sho w that the oxidation proceeds by way of a diffusion-controlled reactio n for Mn2+ ions located at B sites and by a nucleation-growth mechanis m for Mn2+ ions located at A sites. The difference in the kinetics beh avior has been attributed to a structural change cation-deficient spin el into multi-phase oxides induced by oxidation temperature.