Synchrotron X-ray absorption of LaCoO3 perovskite

LaCoO3 perovskite was prepared at 700degreesC using citrate precursors. The product was then characterized with X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). The powder XRD pattern indicates rhomboliedral (R (3) over barc) or its monoclinic I2/a subgroup symmetry. The electronic configuration and the short-range atomic structure of the LaCoO3 perovskite at room temperature were investigated using synchrotron near-edge X-ray absorption spectroscopy (XANES) and extended X-ray absorption spectroscopy (EXAFS). From the XANES region of the XAS we conclude that Co(III) is at least partly in its intermediate- or high-spin state, which is in accordance with most of the published literature on LaCoO3 perovskite. The EXAFS region of the LaCoO3 perovskite spectrum, which up to now was almost not investigated, was simulated satisfactorily for the first two radial structure peaks in terms of the dominant scattering contributions generated with the FEFF8 code and the structural information available from crystallographic data. The best simulation results were obtained with I2/a symmetry. The obtained amplitude reduction factor, zero-energy shift and Debye-Waller factors are useful reference values for data analyses of similar compounds like partly substituted LaCoO3 perovskite, such as La1-xCaxCoO3 or La1-xSrxCoO3, which are materials of technical interest in catalyst and other applications. (C) 2003 Elsevier Inc. All rights reserved.