本論文的工作是利用X光吸收光譜研究Ca3Co4O9及其相關材料的電子結構，以探討電洞的濃度與熱電性質的關係。在以鐵取代部分的鈷原子系統中，隨著鐵的量變多鐵的L3-edge的空軌域有逐漸增加的趨勢，而由氧的前置吸收峰可知O 2p與過渡金屬3d混成軌域隨著鐵的增加空軌域有上升的趨勢，而當鐵掺雜等於0.05時鈷原子有最少的未佔據態，比照熱電功率與電阻率的實驗數據可發現：鈷的未佔據態少則熱電功率越好。在以錳取代部份的鈷原子系統中，隨著錳的增加，由氧的前置吸收峰可知O 2p與過渡金屬3d混成的空軌域有減少的趨勢，且鈷的L3-edge空軌域隨著錳的增加而逐漸減少。比照熱電功率與電阻率的實驗數據得鈷的未佔據態少則熱電功率越好。在這些系統中鈷的平均價數大約為3.50價，鐵平均價數大約為3.00價，錳的平均價數大約為3.06價。 In order to study the correlation between hole concentration and the thermoelectric property, we have performed x-ray absorption near edge structure (XANES) study of Ca3Co4O9 based thermoelectric materials. In Fe-doped systems, the Fe unoccupied states can be increased by increasing the Fe concentration. On the other hand, O K-edge prepeak shows the electric structure of transition metal 3d-O 2p hybridization increased by increasing Fe concentration. The Co have lessed unoccupied states when Fe-doped equal to 0.05. That compare with thermoelectric data . We find the lesser Co unoccupied states the more thermoelectric power. In Mn-doped systems, transition metal 3d-O 2p hybridization decreased by increasing Mn concentration. So does Co unoccupied states. And we find the lesser Co unoccupied states the more thermoelectric power. We also observed that the average valence of Co in Ca3Co4-xMxO9 (M=Fe, Mn) are about 3.50+. The average valence of Fe and Mn are about 3.00+ and 3.06.
