淡江大學機構典藏:Item 987654321/87401
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    Title: 以X光吸收光譜研究稀土元素摻雜對CaMnO3電子結構之影響
    Other Titles: Effect of rare-earth-doping on the electronic structure of CaMnO3 studied by X-ray absorption spectroscopy
    Authors: 吳美惠;Wu, Mei-Huei
    Contributors: 淡江大學物理學系碩士班
    張經霖;Chang, Ching-Lin
    Keywords: X光吸收光譜;稀土元素;x-ray absorption spectroscopy;CaMnO3
    Date: 2012
    Issue Date: 2013-04-13 11:03:09 (UTC+8)
    Abstract: 我們利用X光吸收光譜研究以稀土元素摻雜取代Ca的CaMnO3熱電材料之電子結構。摻入的元素包含 Sm、Eu、Gd、Dy，其摻雜量均為0.02，及改變其中一個元素Gd濃度的摻雜量0.02及0.05取代Ca。從O K-edge光譜中可看出摻雜不同稀土元素後吸收強度變大即Mn 3d與O 2p的混成程度增加了；從Mn K-edge光譜中發現Mn 4p的空軌域數在摻雜後強度都增強；從Mn L2,3-edge光譜可看出摻雜後Mn 3d空軌域數均增加；從Ca L2,3-edge光譜中發現Ca 3d空軌域數目在摻雜後皆減少。摻雜的稀土元素價數都比Ca大，改變了Mn 3d的電子組態；而且都由離子半徑較小的稀土元素取代離子半徑較大的Ca，拉近了MnO2層之間的距離使Mn-O混成程度增高，導電性變好，電阻率變低。在這系統中Mn的平均價數為3.8價。
    We use the X-ray absorption spectra studied the electronic structure of rare earth elements doping the thermoelectric materials CaMnO3 replaced the Ca materials. The incorporation elements included Sm, Eu, Gd, Dy, and the doping concentration ratio was 0.02. We changed one of the elements Gd doping concentration to 0.05 replaced Ca elements. From O K-edge spectrum can be seen that larger the Mn 3d and O 2p hybrid extent and increased absorption intensity by doping different rare earth; From Mn K-edge spectra of doping rare earth elements, we can find the Mn 4p unoccupied state all increased and from Mn L2 ,3-edge spectra, the Mn 3d unoccupied state all increased too. From Ca L2, 3-edge spectra, the Ca 3d unoccupied state all decreased after doping rare earth elements.
    The valence of doping rare earth elements larger than the element Ca and changed the electronic configuration of Mn 3d; smaller ionic radius of rare earth elements replaced larger ionic radius Ca elements that closer to the distance between MnO2 layers, and increased the Mn-O hybrid extent.
    The conductivity become better and low resistivity. The average valence of Mn is 3.8 in this system.
    Appears in Collections:[Graduate Institute & Department of Physics] Thesis

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