article
XAS structural characterization of La1xAxCoO3 doped with calcium and barium as a function of temperature
Registro en:
0301-0104
10.1016/j.chemphys.2017.04.008
Autor
Melo, Marcus Antônio de Freitas
Gomes, Washington C.M.
Melo, Dulce Maria de Araújo
Pimentel, Washington C.
Marinho, Érika Pinto
Nasar, Ricardo Silveira
Resumen
The temperature dependence of La0.8Ba0.2CoO3 and La0.8Ca0.2CoO3 perovskite structures was investigated, and the LaCoO3 structure was analyzed at room temperature. These materials were characterized by X-ray absorption spectroscopy (XAS) at the cobalt K-edge, and both the X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) data were analyzed. The correlated Einstein model was used in the EXAFS data analysis. These materials were prepared by the combustion method. The structures of LaCoO3 at room temperature and of the Ca2+- and Ba2+-doped samples in the temperature range of 50 K–298 K the CoO6 octahedron have a distorted monoclinic I2/a symmetry. However, the Ba2+-doped sample the CoO6 octahedron has a slightly distorted rhombohedral R-3c symmetry at 50 K, 220 K and 260 K. The La0.8Ca0.2CoO3 structure does not vary much with temperature and
has a more distorted Co octahedron and higher local thermal disorder