In situ XPD studies of nanocrystalline CeO2-Fe2O3 ceramics

M. MAZAN; T. S. MARTINS; D.G. LAMAS; S.A. LARRONDO

Campinas

Congreso; 24ª Reunião anual de usuários do LNLS/CNPEM; 2014

LNLS

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 CeFeO2-x 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 CeO2 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 every sample. 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.