Structural and morphological properties of Ce(1-x)FexO2-δ synthesized by citrate route

MARIANO MAZÁN; ALDO F. CRAIEVICH; EMILIA B. HALAC; DIEGO G. LAMAS; S.A. LARRONDO.

Encuentro; XIV Brazilian MRS meeting; 2015

Cerium-based materials have been intensively studied in the last years because oftheir high oxygen storage capacity (OSC) associated to the reversibleCe4+↔Ce3+ process. The properties of ceria-based materials are closely relatedto their defect chemistry, which is determined by concentration, size and chargeof dopant cations. Fe3+cation is an interesting candidate as doping agentbecause its effective ionic radius is smaller than that of Ce4+. In this workCe(1-x)FexO2-δ mixed oxides with different iron content (x=0, 0.05, 0.10, 0.15,0.20, 0.30, 0.5, 0.7, 1) were synthesized by the so named ?citrate method?. Thismethod of synthesis yields very small particles in the nanoscale range. Nanosizedcerium crystals were established to be good as hosts for iron oxide, retaining the cubic structure of undoped ceria even after incorporation up to 30 at.% of iron.Our results of X-ray diffraction and Raman experiments suggest that thisincorporation exhibits a competition between location of iron atoms in host cation and interstitial sites, depending on iron doping level. Besides, Ramanspectroscopy evidenced the formation of a small volume fraction of hematiteclusters in samples with relatively high iron content, x≥0.15 but segregation ofhematite was observed in X-ray diffraction experiments only for samplescontaining 50 and 70% of iron. The solid solutions exhibit high porosity and also high specific surface area, with nearly 10% of pore volume in the micropore size range. These morphological properties make these materials potentially useful for applications in catalysis.