Melo, Dulce Maria de AraújoGomes, Washington Charles de Macedo2014-12-172014-04-082014-12-172013-09-09GOMES, Washington Charles de Macedo. Caracterização estrutural de Perovskitas Lax-1AxCoO3 (x=0 e 0,2) ,dopadas com cálcio e bario, por espectroscopia de absorção de raios X (XAS).. 2013. 74 f. Tese (Doutorado em Físico-Química; Química) - Universidade Federal do Rio Grande do Norte, Natal, 2013.https://repositorio.ufrn.br/jspui/handle/123456789/17779In this work, the structures of LaCoO3, La0,8Ba0,2CoO3 and La0,8Ca0,2CoO3 perovskites were characterized as a function of temperature (LaCoO3 structure being analyzed only at room temperature). The characterization of these materials were made by X-Ray Absorption Spectroscopy (XAS), in the cobalt K-edge, taking into account the correlated Einstein model X-ray absorption fine structure (EXAFS). The first part of the absorption spectrum corresponded the X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). These materials were prepared by the combustion method. The combustion products were calcinated at 900 0C, for 6 hours in air. Noted that the sample LaCoO3 at room temperature and samples doped with Calcium and Barium in the temperature range of 50 K to 298 K showed greater distortion to monoclinic symmetry with space group I2/a. However, the sample doped with barium at the temperatures 50 K, 220 K, and 260 K showed a slight distortion to rhombohedral symmetry with space group R-3c. The La0,8Ca0, 2CoO3 structure was few sensitive to temperature variation, showing a higher local distortion in the octahedron and a higher local thermal disorder. These interpretations were in agreement with the information electronic structural on the XANES region and geometric in the EXAFS regionapplication/pdfAcesso AbertoQuímica inorgânica. Físico-química. Espectroscopia de absorção de raios X (XAS). LaCoO3 La0. 8Ba0. 2CoO3. La0. 8Ca0. 2CoO3X-ray absorption spectroscopy. LaCoO3. La0. 8Ba0. 2CoO3. La0. 8Ca0. 2CoO3. Temperature. Spin transition. Combustion synthesisdoctoralThesisCNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA