Mixed Co,Fe oxides prepared by thermal or mechanical treatment of carbonate precursors

Mixed Fe,Co oxides are prepared by thermal or mechanochemical decomposition of mixed carbonate precursors. The thermal decomposition of carbonates at 300°C in air gives single-phase cation-deficient spinels encompassing the whole range of compositions. These samples show high dispersity and have lattice distortions particularly in the range 0.523–0.646 (Co/(Co+Fe)). The oxides prepared at 600°C are mixtures of Co₃O₄/CoFe₃O₄ for that composition interval. A decrease in cation vacancy content and an increase in the unit cell parameters are observed at this temperature. The mechanochemical decomposition of the carbonate precursors takes place after longer grinding times for Co-rich samples, which give Fe,Co-mixed monoxides. The Fe-rich samples give spinel oxides.