6533b7d8fe1ef96bd1269a27

RESEARCH PRODUCT

Analysis of the oxidation process and mechanical evolution in nanosized copper spinel ferrites. Role of stresses on the coercivity

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Isothermal oxidations of the iron(II) and copper(I) cations in nanosized copper spinel ferrites which were oxidized in cation-deficient spinels have been studied by thermogravimetric analysis. The low temperature kinetics of oxidation of each oxidizable cation has been explained on the basis of a diffusion-induced stress effect, these stresses being generated in the ferrite particles by the chemical gradient induced during the oxidation process where the cations at the surface are more oxidized than those in the bulk. A reaction mechanism coupling the chemical and the mechanical effects has been proposed. When the Cu-ferrites contain some Co-cations, it has also been revealed that the stresses have a significant influence on the enhancement of the coercivity.