Synthesis and characterization of manganese-cobalt solid solutions prepared at low temperature

Abstract

Two extreme compositions of the manganese-cobalt oxide system Mn xCo3-xO4 namely Co3O4 (x = 0) and MnCo2O4 (x = 1) were prepared in powder form at low temperature by thermal decomposition of nitrates in air. The synthesis was conducted at 150°C. The oxides obtained were characterized by different techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), surface area determination using the Brunauer-Emmett-Teller (BET) method, thermogravimetric analyses (TGA) and oxidation power (OP). XRD analysis reveals that the oxides crystallize in a cubic spinel-type structure with a unit cell parameter (ao) that increases as cobalt is replaced by manganese. The MnCo2O4 showed 70 m2 g-1 and 13 nm of specific surface area and crystallite size respectively. The crystallite was bigger (20nm) when cobalt-manganese oxide is prepared as a thin film. Both compounds exhibited nanometric size. The cationic distributions proposed for both oxides on the basis of the physicochemical characterization results showed an excellent agreement with those obtained from the XRD data refinement performed using the Rietveld method.