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    Title: X-ray absorption spectroscopy studies of Ca2.9Ln0.1Co4O9+δ (Ln = Ca, Dy, Ho, Er and Lu)
    Authors: Chen, J.L.;Liu, Y.S.;Liu, Chia-Jyi;Nong, N.V.;Kao, Y.C.;Chen, C.C.;Wang, W.C.;Chen, S.S.;Chen, C.L.;Dong, C.L.;Chang, C.L.
    Contributors: 淡江大學物理學系暨研究所
    Keywords: Thermoelectric materials;X-ray absorption spectroscopy;Thermoelectric power;Cobaltite
    Date: 2012-07
    Issue Date: 2014-03-06 16:02:02 (UTC+8)
    Publisher: Amsterdam: Elsevier BV
    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+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 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.
    Relation: Journal of Alloys and Compounds 529, pp.8-11
    DOI: 10.1016/j.jallcom.2012.03.052
    Appears in Collections:[物理學系暨研究所] 期刊論文

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