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    Title: Xray Absorption Fine Structure (XAFS) Study of the High-Tc Superconductor Pb-Bi-Sr-Ca-Cu-O System = 方向性X光吸收光譜對Pb-Bi-Sr-Ca-Ca-Cu-O研究
    Authors: 彭維鋒;Pong, Way-faung;周鑑恆;Chou, C. H.;林諭男;Lin, I. N.;蔡尚芳;Tsai, S. F.
    Contributors: 淡江大學物理學系
    Date: 1991-06
    Issue Date: 2009-12-31 11:00:23 (UTC+8)
    Publisher: 中華民國物理學會
    Abstract: Samples of (PbxBi2-x)Sr2Ca2Cu3Oy were prepared with appropriate proportions of PbO, Bi2O3, SrCO3, CaCO3 and CuO powders. For the high-Tc superconductive samples in which x = 0, 0.2, 0.4, 0.6, we have measured the XAFS spectra of the Cu K-edge, the Pb L3-edge and the Bi L3-edge at room temperature in the transmission mode at NSLS using the X-23 beamline. The results of our study indicate that: (1) Pb atoms within PbO partially substitute for Bi atoms in Bi-Sr-Ca-Cu-0 superconductors; (2) there is evidence for the existence of unreacted PbO, particularly in the sample in which x = 0.6; (3) the oxidation number of most Pb ions in the Bi site within the Bi-Sr-Ca-Cu-0 system remains 2; (4) a sufficient proportion of PbO is essential for the formation of the high-Tc phase, (5) and the addition of PbO is responsible only for the phase transformation of the low-Tc phase into the high-Tc phase. Moreover, the electronic structure of the Cu-0 layers is essentially independent of the Pb substitution. The oxidation number of Cu ions in the high-Tc phase is slightly larger than that of Cu ions in the low-T, phase, and the average oxidation number of Bi remains nearly constant independent of either the phase transformation or Pb substitution. We have also deduced that the Cu-0 layers have an ordered structure, and comment qualitatively about the incommensurate modulations in the Bi-0 layers.
    Relation: Chinese Journal of Physics=中國物理學刊 29(3),頁263-282
    Appears in Collections:[物理學系暨研究所] 期刊論文

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