Thermal and spectroscopic study on the solid-solid interaction between CuO and Fe2O3 and the effect of sodium ions

CuO-Fe₂O₃ sample of equimolar ratio was prepared by coprecipitation. The mixed hydroxides were studied using differential thermal analysis. The thermal products at different temperatures up to 1000°C were characterized by means of X-ray diffraction analysis. The morphological changes were followed through scanning electron microscopy and complemented by X-ray photoelectron spectroscopy. The thermal treatment of the mixed hydroxides at temperatures between 200 and 1000°C produced almost a crystalline CuO-phase. Scanning electron microscopy showed two distinct types of species. The first (major) is microspheres and the second is needle-like type. Electron spectroscopy for chemical analysis revealed that this sample contained sodium ions which covered the surface of the CuO-Fe₂O₃ species in the form of sodium sulphate layer. This layer prevents the solid-solid interaction. Washing the sample thoroughly leads to the removal of sodium sulphate layer and increases the reactivity of solids to form a crystalline copper-ferrite phase.