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Publication Detail
Phase separation and surface segregation in ceria-zirconia solid solutions
  • Publication Type:
    Journal article
  • Publication Sub Type:
    Article
  • Authors:
    Grau-Crespo R, de Leeuw NH, Hamad S, Waghmare UV
  • Publisher:
    ROYAL SOC
  • Publication date:
    08/07/2011
  • Pagination:
    1925, 1938
  • Journal:
    P ROY SOC A-MATH PHY
  • Volume:
    467
  • Issue:
    2131
  • Print ISSN:
    1364-5021
  • Language:
    EN
  • Keywords:
    ceria-zirconia, phase separation, surface segregation, solid solution, density functional theory, YTTRIA-STABILIZED ZIRCONIA, OXYGEN STORAGE CAPACITY, CEO2-ZRO2 MIXED OXIDES, NEAR-CRITICAL WATER, LOW-INDEX SURFACES, ONE-STEP SYNTHESIS, ELECTRONIC-STRUCTURE, COMPUTER-SIMULATION, ZRO2-CEO2 SYSTEM, REDUCTION
  • Addresses:
    Grau-Crespo, R
    UCL
    Dept Chem
    London
    WC1H 0AJ
    England

    Univ Pablo de Olavide
    Dept Phys Chem & Nat Syst
    Seville
    41013
    Spain
Abstract
Using a combination of density functional theory calculations and statistical mechanics, we show that a wide range of intermediate compositions of ceria-zirconia solid solutions are thermodynamically metastable with respect to phase separation into Ce-rich and Zr-rich oxides. We estimate that the maximum equilibrium concentration of Zr in CeO2 at 1373K is approximately 2 per cent, and therefore, equilibrated samples with higher Zr content are expected to exhibit heterogeneity at the atomic scale. We also demonstrate that in the vicinity of the (111) surface, cation redistribution at high temperatures will occur with significant Ce enrichment of the surface, which we attribute to the more covalent character of Zr-O bonds compared with Ce-O bonds. Although the kinetic barriers for cation diffusion normally prevent the decomposition/segregation of ceria-zirconia solid solutions in typical catalytic applications, the separation behaviour described here can be expected to occur in modern three-way catalytic converters, where very high temperatures are reached.
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