Synchrotron XRD Study of ZrO2-CeO2 Nanopowders Synthesised by Gel-combustion

D.G. LAMAS; R.O. FUENTES; I.O. FÁBREGAS; M.E. RAPP; G.E. LASCALEA; J.R. CASANOVA; N.E. WALSÖE DE RECA; A.F. CRAIEVICH

Florencia, Italia

Congreso; XX Congress of the International Union of Crystallography and General Assembly; 2005

International Union of Crystallography

Resumen publicado en Acta Cryst. (2005). A61, C486 Zirconia-ceria solid solutions are being widely investigated due to their excellent mechanical and catalytic properties. For example, these materials are extensively used as promoters in three-way catalysts. In this work, the crystal structure of nanocrystalline ZrO2-CeO2 solid solutions, synthesised by a pH-controlled nitrate-glycine gelcombustion process, has been studied by using a high-intensity synchrotron X-ray diffractometer (D12A-XRD1 beamline of the LNLS, Brazilian Light Facility). Several weak Bragg peaks of the tetragonal phase, which correspond to forbidden reflections in the case of a perfect cubic fluorite structure, were detected. By determining theintegrated intensity of the strongest of these reflections, (112), as a function of the CeO2 content, the tetragonal-cubic phase compositional boundary was established to be at (85 +/- 5) mol% CeO2. For a CeO2 content up to (68 +/- 2) mol%, we identified a tetragonalphase with c/a > 1, whereas, in the range between 68 and 85 mol% CeO2, the existence of a tetragonal phase with c/a = 1 and oxygen anions displaced from their ideal positions in the cubic phase (keeping the tetragonal symmetry) was verified. Finally, solid solutions with CeO2 contents higher than 85 mol% exhibit the cubic fluorite-type phase.