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

Abstract

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.

Authors:
;
Publication Date:
Research Org.:
Argonne National Lab., IL (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
11895
Report Number(s):
ANL/IPNS/CP-99536
TRN: AH200119%%101
DOE Contract Number:  
W-31109-ENG-38
Resource Type:
Conference
Resource Relation:
Conference: 22nd Rare Earth Research Conference, Argonne, IL (US), 07/10/1999--07/15/1999; Other Information: PBD: 16 Jul 1999
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 33 ADVANCED PROPULSION SYSTEMS; CATALYTIC CONVERTERS; CATALYSTS; IONIC CONDUCTIVITY; NEUTRON DIFFRACTION; CRYSTAL-PHASE TRANSFORMATIONS; REDOX POTENTIAL; DOPED MATERIALS; ZIRCONIUM OXIDES; CERIUM OXIDES; LANTHANUM; NEODYMIUM; CRYSTAL DEFECTS

Citation Formats

Loong, C -K, and Ozawa, M. The role of rare-earth dopants in nanophase zirconia catalysts for automotive emission control.. United States: N. p., 1999. Web.
Loong, C -K, & Ozawa, M. The role of rare-earth dopants in nanophase zirconia catalysts for automotive emission control.. United States.
Loong, C -K, and Ozawa, M. 1999. "The role of rare-earth dopants in nanophase zirconia catalysts for automotive emission control.". United States. https://www.osti.gov/servlets/purl/11895.
@article{osti_11895,
title = {The role of rare-earth dopants in nanophase zirconia catalysts for automotive emission control.},
author = {Loong, C -K and Ozawa, M},
abstractNote = {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.},
doi = {},
url = {https://www.osti.gov/biblio/11895}, journal = {},
number = ,
volume = ,
place = {United States},
year = {1999},
month = {7}
}

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