ZrO2-CeO2 solid solutions synthesized by different chemical routes: crystal structure and local order

L.M. ACUÑA; M.G. ZIMICZ; D. LAMAS; R.O. FUENTES; S. LARRONDO; M.C.A. FANTINI; A.F. CRAIEVICH

Campinas

Congreso; 19º Reunión Anual de Usuarios (RAU); 2009

LNLS

ZrO2-CeO2 substitutional solid solutions have found application as redox or oxygen storage promoters in three-way catalysts because of their high oxygen storage capacity (OSC). Also, due to their excellent catalytic properties for direct oxidation of hydrocarbons, these materials have been proposed as anodes in intermediate temperature solid oxide fuel cells (IT-SOFCs). In particular, the electrical and catalytic properties are close related to the crystal structure of the powders. In previous XRD studies at LNLS, we found a tetragonal-to-cubic transition as a function of composition and also a tetragonal-to-cubic phase transition as function of temperature in ZrO2-50 and 65 mol% CeO2 nanopowders. In both cases, the cation-oxygen bond was also studied by EXAFS, finding a correlation between the structural and local changes. In this work, we studied the influence of the synthesis methods on the structure and local order of ZrO2-50, 70 and 90 mol% CeO2  nanopowders. Compositionally homogeneous nanopowders were synthesized by gel-combustion and citrate complexation methods. Measurements were carried out at the D10B-XPD and D04B-XAFS1 beamlines of the LNLS. We found that the crystallite size and morphology of the powders have been strongly influenced by the synthesis method. Lattice parameters were refined by Rietveld method and local order around Zr cations were studied.