Mechanism and Cationic Rearrangements Involved in the Reduction of Co2+[Co2-x3+Crx3+]O42− Spinels
This work deals with the Co(II, III)-Cr(III) oxide series (or Co3O4-CoCr2O4 solid solutions) with compositions ranging from Co3O4 to CoCr2O4. These oxides crystallize in the spinel structure and, according to Makkonen, their lattice parameter increases linearly with their Cr content from 8.08 Å for Co3O4 to 8.33 Å for CoCr2O4 (1). They are paramagnetic above Tc(CoCr2O4) = 100°K and TN (Co3O4) = 40°K. From their Curie constants we show that the Co3+ ions have a zero magnetic moment and, thus, are in a low spin state in octahedral sites (B), the moment of tetrahedral (A) Co2+ being 4.6 ~ 4.7 µ B. Whence the formula:
KeywordsOctahedral Site Spinel Structure Hydrogen Reduction Curie Constant Oxide Series
Unable to display preview. Download preview PDF.