X-ray absorption spectroscopy studies of Ca 2.9Ln 0.1Co 4O 9+δ (Ln = Ca, Dy, Ho, Er and Lu)

J. L. Chen, Y. S. Liu, Chia Jyi Liu, N. V. Nong, Y. C. Kao, C. C. Chen, W. C. Wang, S. S. Chen, C. L. Chen, C. L. Dong, C. L. Chang

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Abstract

X-ray absorption near edge structure (XANES) study of Co K-, Co L 2,3-, O K-, and Ca L 2,3-edges on a series of polycrystalline Ca 2.9Ln 0.1Co 4O 9+δ (Ln = Ca, Dy, Ho, Er and Lu) are presented. The high similarity of Co K-edge spectra of the doped and the undoped samples indicate that the average valence of Co is slightly higher than 3+ and it is not varied for different dopants. The variation of the intensity of the Co L 2,3-edge indicates that the number of Co 3d unoccupied states and thermoelectric power shows an opposite trend. According to the O K-edge spectra, the electrical resistivity and Co 4+ 3d-O 2p hybridized unoccupied states also show an opposite trend, which is consistent with our results that a lesser amount of Co 4+ leads to a larger thermoelectric power. There is a monotonic decrease of Ca L 2,3-edge intensity with decreasing ionic radius of the Ln element, which partially substituted for Ca. This could be attributed to a decrease of Ca 3d-O 2p hybridization with decreasing ionic radius of Ln.

Original languageEnglish
Pages (from-to)8-11
Number of pages4
JournalJournal of Alloys and Compounds
Volume529
DOIs
Publication statusPublished - 2012 Jul 15

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All Science Journal Classification (ASJC) codes

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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