Production of strontium-substituted lanthanum manganite perovskite powder by the amorphous citrate process

The amorphous citrate process has been used to produce Mn₂O₃, Mn₃O₄, LaMnO₃, SrMnO₃ and strontium-substituted LaMnO₃. The citrate-nitrate gels were dehydrated at 70 C to yield solid precursor materials. The decomposition/oxidation of the precursors have been studied using thermogravimetry and evolved gas analysis. The products of decomposition have been characterized by X-ray diffraction analysis, scanning electron microscopy and, in the case of the strontium-substituted LaMnO₃, by analytical electron microscopy. The surface area and residual carbon content of the strontium-substituted LaMnO₃ have been determined as a function of the decomposition/oxidation temperature. Both the process yield and compositional homogeneity of the strontium-substituted LaMnO₃ have been shown to increase as the decomposition temperature increases. The residual carbon content has been shown to decrease as decomposition temperature increases. However, the surface areas of the powders decrease significantly as decomposition temperature increases. Consequently, it is evident that there is a conflict in the experimental conditions required for optimum yield, homogeneity and residual carbon content compared to those required for maximum surface area.