X-ray absorption spectroscopy studies of Ca2.9Ln0.1Co4O9+δ (Ln = Ca, Dy, Ho, Er and Lu)

J.L. Chen, Y.S. Liu, Chia-Jyi Liu, Ngo Van Nong, Y.C. Kao, C.C. Chen, W.C. Wang, S.S. Chen, C.L. Chen, C.L. Dong, C.L. Chang

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

X-ray absorption near edge structure (XANES) study of Co K-, Co L2,3-, O K-, and Ca L2,3-edges on a series of polycrystalline Ca2.9Ln0.1Co4O9+ı (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 L2,3-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 Co4+ 3d–O 2p hybridized unoccupied states also show an opposite trend, which is consistent with our results that a lesser amount of Co4+ leads to a larger thermoelectric power. There is a monotonic decrease of Ca L2,3-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. © 2012 Elsevier B.V. All rights reserved.
Original languageEnglish
JournalJournal of Alloys and Compounds
Volume529
Pages (from-to)8-11
ISSN0925-8388
DOIs
Publication statusPublished - 2012
Externally publishedYes

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