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 1/2La(2)O(3) and CoO, the calcination of coprecipitates of 1/2La(2)(C2O4)(3).nH(2)O and CoC2O4.mH(2)O, and the thermal decomposition of a heteronuclear complex La[Co(C2O4)(3)].8.5H(2)O. 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 degreesC 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 degreesC after the preparation by the heteronuclear complex decomposition were lower by about one order than. those of LaCoO3 sintered from the mixture of 1/2La(2)O(3) and CoO and the coprecipitates of 1/2La(2)(C2O4)(3).nH(2)O and CoC2O4.mH(2)O, whereas the densities are similar to each other regardless of the preparation methods. (C) 2002 Elsevier Science B.V. All rights reserved.