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    Title: X光吸收光譜對錳摻雜之NaCo2O4的研究
    Other Titles: X-ray absorption spectroscopy study of manganese doped NaCo2O4
    Authors: 施政行;Shih, Jeng-shyng
    Contributors: 淡江大學物理學系碩士班
    張經霖;Chang, Ching-lin
    Keywords: 延伸X光吸收光譜精細結構;X光吸收光譜近邊緣結構;熱電材料;NaCo2O4;EXAFS;XANES;Thermoelectric materials;NaCo2O4
    Date: 2005
    Issue Date: 2010-01-11 02:15:14 (UTC+8)
    Abstract: 本論文的是利用X光吸收光譜研究在1%氧分壓下燒結的NaCo2-XMnXO4材料的電子結構,以探討電洞的濃度和熱電性質的關係。由Co與Mn的K-edge EXAFS證實Mn的摻雜有取代Co在NaCo2-XMnXO4結構中所在的位置;在Co與Mn的K-edge光譜可知,在不同的Mn摻雜量下,Co的平均價數是+3.3價,而Mn則是+3.6價,且NaCo2-XMnXO4系列樣品皆遵守電中性平衡。由O的K-edge前吸收峰顯示O 2p – Co 3d – Mn 3d的混層電子結構,在Mn的摻雜含量x=0.10以下時,電子組態有多重結構,當Mn的摻雜量到達x=0.15時,在Co 3d只有單一吸收峰,所以Co的電子是低自旋組態。且由O 2p – Co 3d – Mn 3d的混成未佔據態空軌域數目,發現NaCo2-XMnXO4的電阻率變化主要受其影響;由Co的L-edge吸收光譜的結果得Co L-edge的譜形變化不明顯,所以Co的3d軌域電子結構沒有改變,但由O 2p – Co 3d – Mn 3d的混成軌域譜形發現與樣品的熱電力有相互關係。
    In order to study the correlations between hole concentration and the thermoelectric property, we have performed X-ray absorption near edge structure (XANES) and Extended X-ray absorption fine structure (EXAFS) to study on Mn doped NaCo2O4 based thermoelectric materials. NaCo2-XMnXO4 are sintered in 1% oxygen partial pressure. From Co and Mn K-edge EXAFS, When Mn doped in NaCo2O4, Mn are substituted for Co. From Co and Mn K-edge XANES, the average valence of Co is 3.3+ and the average valence of Mn is 3.6+. With Mn concentration increased, O K-edge prepeak show the different electric structure of O 2p - Co 3d - Mn 3d hybridization. O K-edge prepeak light shapes are related to thermopower. From O 2p - Co 3d - Mn 3d hybridization unoccupied states and Co L3-edge unoccupied states, the results indicate that unoccupied states are related to resistivity of NaCo2-XMnXO4 .
    Appears in Collections:[物理學系暨研究所] 學位論文

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