The role of rare-earth dopants in nanophase zirconia catalysts for automotive emission control.

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Rare earth (RE) modification of automotive catalysts (e.g., ZrO{sub 2}) for exhaust gas treatment results in outstanding improvement of the structural stability, catalytic functions and resistance to sintering at high temperatures. Owing to the low redox potential of nonstoichiometric CeO{sub 2}, oxygen release and intake associated with the conversion between the 3+ and 4+ oxidation states of the Ce ions in Ce-doped ZrO{sub 2} provide the oxygen storage capacity that is essentially to effective catalytic functions under dynamic air-to-fuel ratio cycling. Doping tripositive RE ions such as La and Nd in ZrO{sub 2}, on the other hand, introduces oxygen vacancies ... continued below

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22 p.

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Loong, C.-K. & Ozawa, M. July 16, 1999.

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Rare earth (RE) modification of automotive catalysts (e.g., ZrO{sub 2}) for exhaust gas treatment results in outstanding improvement of the structural stability, catalytic functions and resistance to sintering at high temperatures. Owing to the low redox potential of nonstoichiometric CeO{sub 2}, oxygen release and intake associated with the conversion between the 3+ and 4+ oxidation states of the Ce ions in Ce-doped ZrO{sub 2} provide the oxygen storage capacity that is essentially to effective catalytic functions under dynamic air-to-fuel ratio cycling. Doping tripositive RE ions such as La and Nd in ZrO{sub 2}, on the other hand, introduces oxygen vacancies that affect the electronic and ionic conductivity. These effects, in conjunction with the nanostructure and surface reactivity of the fine powders, present a challenging problem in the development of better ZrO{sub 2}-containing three-way catalysts. We have carried out in-situ small-to-wide angle neutron diffraction at high temperatures and under controlled atmospheres to study the structural phase transitions, sintering behavior, and Ce{sup 3+} {leftrightarrow} Ce{sup 4+} redox process. We found substantial effects due to RE doping on the nature of aggregation of nanoparticles, defect formation, crystal phase transformation, and metal-support interaction in ZrO{sub 2} catalysts for automotive emission control.

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22 p.

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OSTI as DE00011895

Medium: P; Size: 22 pages

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  • 22nd Rare Earth Research Conference, Argonne, IL (US), 07/10/1999--07/15/1999

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  • Report No.: ANL/IPNS/CP-99536
  • Grant Number: W-31109-ENG-38
  • Office of Scientific & Technical Information Report Number: 11895
  • Archival Resource Key: ark:/67531/metadc621281

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  • July 16, 1999

Added to The UNT Digital Library

  • June 16, 2015, 7:43 a.m.

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  • April 10, 2017, 3:16 p.m.

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Loong, C.-K. & Ozawa, M. The role of rare-earth dopants in nanophase zirconia catalysts for automotive emission control., article, July 16, 1999; Illinois. (digital.library.unt.edu/ark:/67531/metadc621281/: accessed October 17, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.