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Home  >  Journal list  >  MATERIALS TRANSACTIONS  >  Vol.45  No.10 (2004)  >  pp.2951-2955

MATERIALS TRANSACTIONS
<<Previous article Vol.45  No.10 (2004)   pp.2951 - 2955 Next article>>

Valence Change of Cations in Ceria-Zirconia Solid Solution Associated with Redox Reactions Studied with Electron Energy-Loss Spectroscopy

Shigeo Arai1), Shunsuke Muto2), Junya Murai3), Tsuyoshi Sasaki4), Yoshio Ukyo4), Kotaro Kuroda2) and Hiroyasu Saka3)
1) 1MV Electron Microscopy Laboratory, Eco Topia Science Institute, Nagoya University
2) Department of Materials, Physics and Energy Engineering, Nagoya University
3) Department of Quantum Engineering, Nagoya University
4) Toyota Central R&D Laboratories


It has been known that the ceria-zirconia solid solutions (Ce2Zr2O7+x, 0 ≤ x ≤ 1) have an excellent ability for oxygen absorption/release. The local charge states of cations in the CeO2-ZrO2 solid solutions have been studied by means of electron energy-loss spectroscopy (EELS) attached to a transmission electron microscope. The relative intensity of cerium-M4,5 white-line peaks from Ce2Zr2O7, Ce2Zr2O7.5 and Ce2Zr2O8 showed a systematic change, which corresponded to the valence change of cerium; Ce3+ in Ce2Zr2O7, Ce4+ in Ce2Zr2O8. By contrast, the valence of the zirconium ions, which are mainly at the nearest neighbor sites of absorbed or emitted oxygen atoms, remains to be quaternary irrespective of oxygen contents. It was found that the energy-loss near edge structure (ELNES) of the cerium-M4,5 edge in Ce2Zr2O7.5 was well reproduced by the sum of the ELNES profiles of Ce2Zr2O7 and Ce2Zr2O8 with an equal weight, the phenomenon of which is known as the ‘valence fluctuation,’ or ‘mixed valence state,’ often observed in rare earth metal compounds.


Keyword:
ceria-zirconia solid solution, pyrochlore structure, electron microscopy, electron energy-loss spectroscopy, white-line, oxygen vacancy, valence fluctuation

Received: May 20, 2004
Accepted: August 18, 2004 , Published online: June 24, 2005
Copyright (c) 2005 The Japan Institute of Metals

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