CO-PRECIPITATION SYNTHESIS OF SOFC ELECTRODE MATERIALS

Six different perovskite-type oxide compositions were investigated: four of them are simple perovskite compounds LaMnO3 (LM), La0.70Sr0.30MnO3-δ (LSM), La0.80Sr0.20FeO3-δ (LSF), La0.75Sr0.25Cr0.50Mn0.50O3-δ (LSCM), and two of them, YBaCo2O5±δ (YBC) and LaBaCo2O5±δ (LBC), belong to the so-called layered perovskite structure; all of them they have been prepared using a carbonate co-precipitation route in aqueous medium. The precipitation yield of the single metal ions has been calculated based on thermodynamic simulation of the precipitation process and compared with the actual yield experimentally determined via chemical analysis of the mother liquors. Upon thermal treatment at high temperature LM, LSM, and LSCM have been obtained as pure phase, YBC and LBC retained traces of impurity phases while LSF was a multiphasic sample. Operating pH higher than 7.5 is suggested to avoid ion losses for all cations, and special attention must be paid when II group elements are involved in the precipitation. Although not conclusive, precipitation equilibria calculation is a useful tool for the ‘a priori’ evaluation of the experimental conditions in the co-precipitation of multi-component oxides.