Synthesis and characterization of nanosized cobalt-manganese spinel oxide

Abstract

Naparticles of cobalt-manganese oxide were prepared by chemical co-precipitation method by decomposition of their respective metal chlorides, sodium carbonate and ethylene diamene tetra acetic acid (EDTA). The heal treatment of the ground precursor powders at their respective decomposition temperature and beyond, results in the evolution of heat from the combustion of the residual carbonaceous material. This facilitates the reaction among the constituent metal ions and the formation of the desired oxide phase at low temperature. The average crystallization size was determined from X-ray diffraction line broadening and the diffractogram was compared with JCPDS data to identify the crystallographic phase of the particle. The shift in (/--value due to the nano nature was also analyzed. The internal elastic micro strain was calculated and it was seen that as the particle size increases strain decreases. The effect of sintering on the particle size was also analyzed. The nano nature of the mixed oxide was also analyzed from the TEM and AFM studies. The FTIR studies have been used to confirm the formation of metal oxide. The characteristic stretching and bending frequencies of the sample were also analyzed. The absorption spectra of the material in the UV-Vis -NIR range were recorded. Strong absorption bands are observed to occur at 550 nm and a weak band around 730nm. From the analysis of absorption spectra, the cobalt-manganese oxide (sintered at 500°, 700° and 900° C) have been found to have direct band gaps ranging from 2.07 to 1.59 eV.