UNIDEF   23986
UNIDAD DE INVESTIGACION Y DESARROLLO ESTRATEGICO PARA LA DEFENSA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
In situ XPD studies of nanocrystalline CeO2-Fe2O3 ceramic
Autor/es:
M. MAZAN; T. MARTINS; D.G. LAMAS; S.A. LARRONDO.
Reunión:
Encuentro; 24º Reunión Anual de Usuarios (RAU), Laboratorio Nacional de Luz Sincrotrón; 2014
Institución organizadora:
LNLS
Resumen:
Although cerium oxide presents good oxygen storage capacity (OSC) and good redox properties, it is not thermally stable. By doping ceria with trivalent ions like Fe the stability could be improved. Samples with different molar percentage ratios (Fe/Ce+Fe named 0Fe, 5Fe, 10Fe, 15Fe, 20Fe and 30Fe) were synthesized by Citrates and Liquid-mix methods and calcined at 623K for 2h. By performing X-ray powder diffraction (XPD) at different temperatures in air at the D10B-XPD beamline of the Brazilian Synchrotron Light Laboratory using a high-intensity and low-resolution configuration the stability of the system ce{CeFeO_{delta}} could be studied. By using the LNLS equipment well resolved patterns and with good intensity, that allowed to perform a good data analysis, were obtained. All the samples showed only the peaks corresponding to the fluorite structure of ce{CeO_2} at room temperature, but only the sample 30Fe presented asymmetric peaks indicating some kind of inhomogeneity or iron segregation. All the samples could be considered monophasic. Segregation of ferric oxide with hematite structure was observed at 923K for 30Fe and at 1073K for the others. All the samples have nanometric crystallite sizes, which showed a continuous growth with temperature as well as the cell parameters. Samples containing iron showed more stable and smaller crystallite sizes than 0Fe. This could be showing that the iron doping is favouring thermal stability.