Preparations of perovskite-type oxides LaCoO3 from three different methods and their evaluation by homogeneity, sinterability and conductivity

Perovskite-type oxide, LaCoO3, was prepared by three different methods that are based on the calcination of a mixture of 1/2La2O3 and CoO, the calcination of coprecipitates of 1/2La2(C2O4)3·nH2O and CoC2O4·mH2O, and the thermal decomposition of a heteronuclear complex La[Co(C2O4)3]·8.5H2O. Thermogravimetric analyses and measurements of infrared spectra and powder X-ray diffraction (XRD) patterns indicated that the formation of LaCoO3 is complete at 1000, 1200 and 600 °C for the respective methods. The electron microprobe analyses showed that the homogeneity is the highest for LaCoO3 obtained from the complex decomposition method. The conductivities of LaCoO3 sintered at 1100–1500 °C after the preparation by the heteronuclear complex decomposition were lower by about one order than those of LaCoO3 sintered from the mixture of 1/2La2O3 and CoO and the coprecipitates of 1/2La2(C2O4)3·nH2O and CoC2O4·mH2O, whereas the densities are similar to each other regardless of the preparation methods.