Figures 1A and 1B show the X-ray diffraction patterns of the Co3O4 and MnCo2O4 phases respectively. Even if the crystalline state is not better defined due to the low temperature of synthesis,Rietveld analysis shows single phases corresponding to the expected compounds which crystallize in the face centered cubic system spinel type, spatial group 7hO (Fd3m). All the main peaks (indicated by their hkl indices) could be indexed by comparison with the diffraction patterns of Co3O4 and MnCo2O4. Both the position and the relative intensities of the diffraction lines were found to be in good agreement with the ASTM X-ray powder data fles JCPDS-ICDD for Co3O4 and MnCo2O4, thus showing that a single phase of each component was present. A remarkable
common feature of the X-ray spectra of both spinel oxides prepared at such a low temperature was the good defnition of the diffraction lines. The mayor peak in both XRD profiles was found to correspond to the (311) crystallographic plane.