Estudio estructural en catalizadores La1-xCaxCoO3-Ć

NORA A. MERINO; LUIS E. CADUS; JULIO ANDRADE GAMBOA

Villa Giardino, Cordoba

Congreso; IX SEMINARIO LATINOAMERICANO DE ANÁLISIS POR TÉCNICAS DE RAYOS X; 2004

Mixed oxides with perovskite type structure (ABO3, ), have important applications, being catalysis one of them. From the ABO3 base structure it is possible to synthesise A1-xA´xB1-yB´yO3±l solid solutions, and since the 90% of the elements can participate in this compounds, it is feasible to obtain a great variety of them. Due to this, the study of the synthesis and structural characterisation of these new materials is interesting for their application as catalysts. Most of the compounds with perovskite type structure have a distortional cubic geometry. For instance, LaCoO3 perovskite has a rhombohedral geometry, the presence of doublet-peaks is characteristic in its difractogram, which in the cubic structure constitute a single peak. This distinction is not clearly seen for small rhombohedral distortions, then, the use of Rietveld method is appropriate for the peaks overlap analysis. The different substitutions in the ABO3 base structure provoke phase transitions and/or modifications in the oxygen stoichiometric and in the cations oxidation states. In this work structural studies of La1-xCaxCoO3-l (x = 0, 0.2, 0.4, 0.5) by means of Rietveld method are discussed.