X光吸收光譜對錳摻雜之NaCo2O4的研究

X-ray Absorption Spectroscopy Study of Manganese Doped NaCo2O4

施政行(Jeng-Shyng Shih)

指導教授 ： 張經霖

淡江大學/理學院/物理學系碩士班/碩士(2005年)

https://doi.org/10.6846/TKU.2005.00193

摘要

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。

關鍵字

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

並列摘要

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 .

並列關鍵字

EXAFS ； XANES ； Thermoelectric Materials ； NaCo2O4

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