尋找無限的能源一直是人類的宿願之一，加上近年來環保意識高漲，許多學者無不投入開發高轉換效率能源材料。熱電材料擁有將熱能與電能互相轉換的優異能力，尤其以廢熱回收(waste heat recovery)蔚為大宗。而在中溫型熱電材料中，CoSb3方鈷礦結構熱電材料擁有極高的發展潛力，經由添加摻雜物改變晶體結構、電子能階與微結構可達到在400 oC ~600 oC之間優異的熱電性質。相圖為熱力學的結晶也是材料科學的基礎，透過相變化、微結構以及組成等種種因素對熱電性質進行進一步的探究，文獻上對於此類資訊描述較少，留下了很多探索方向。因鍺(Germanium)與錫(Tin)有著優異導電性，透過此兩元素的添加進行熱電性質的提升。本研究致力於建立Ge-Sn-Co-Sb四元相圖。本研究的工作包括：(1)以實驗建構Ge-Co-Sb三元液相線投影圖、(2)Sn-Co-Sb三元液相線投影圖，(3)選定化學計量比組成之CoSb3之二元合金，進行熱電性質量測及討論，(4)在CoSb3中摻雜Ge、Sn，並量測熱電性質及討論。由本研究結果可知，Ge-Sn-Co-Sb液相線投影圖由實驗分析，總共存在16個首要析出相區。在熱電性質中，多孔性材料CoSb3在544 K下量測到zT值為0.265，比起單晶CoSb3有著50倍的突破，而在Ge摻雜量為1 %的CoSb3在661 K下量測到0.278的值，最佳熱電優值的表現溫度往較高的溫度偏移，同溫下比起多孔性材料CoSb3有著接近123 %的提升。

Thermoelectric materials and devices can generate electricity from thermal energy directly, and can be useful in waste heat recovery. The skutterudite CoSb3 has been a cost-effective alternative for the mid-temperature thermoelectric generator owing to its promising electrical transport properties. Herein, minor dopant of Ge or/and Sn is introduced into the CoSb3 for optimizing the thermal/electrical transport behaviors. Phase diagram of ternary Sn-Co-Sb and Ge-Co-Sb systems are crucial in illustrating the relationships between the phase stability, microstructures and thermal-to-electricity conversion, and have been determined by experiments. Herein the liquidus projections of ternary Ge-Co-Sb and Sn-Co-Sb system are constructed by collecting the information from various as-solidified Sn-Co-Sb and Ge-Co-Sb alloys. On the basis of as-determined phase diagram, selective ternary Ge-doped/Sn-doped CoSb3 alloys are synthesized and their thermoelectric properties are measured within 300 K-700 K. Among the Ge/Sn-doped CoSb3, the alloy with 1 at% Ge content reaches the highest peak value of zT~ 0.28 at 661 K, showing 123 % enhancement compared with that of undoped CoSb3.

摘要 ii
Abstract iii
一、前言 1
二、文獻回顧 8
2-1熱電元件 8
2-2 CoSb3熱電材料 10
2-3相圖 12
2-4 Co-Ge二元系統相圖 13
2-5 Co-Sb二元系統相圖 15
2-6 Ge-Sb二元系統相圖 17
2-7 Co-Sn二元系統相圖 18
2-8 Sn-Sb二元系統相圖 20
三、實驗方法 22
3-1 Ge-Sn-Co-Sb四元系統之液相線投影圖 22
3-1-1合金配置 22
3-1-2樣品處理與分析 23
3-2 四元Ge-Sn-Co-Sb系統之熱電性質 24
3-2-1 合金配置 24
3-2-2 熱電性質量測 26
四、結果與討論 28
4-1 四元Ge-Sn-Co-Sb系統液相線投影圖 28
4-2 Ge-Co-Sb系統液相線投影圖 30
4-2-1 Co首要析出相區 36
4-2-2 Co3Ge2Sb首要析出相區 38
4-2-3 CoSb首要析出相區 48
4-2-4 CoGe首要析出相區 50
4-2-5 CoGe2首要析出相區 55
4-2-6 CoSb2首要析出相區 64
4-2-7 Ge首要析出相區 70
4-2-8 CoSb3首要析出相區 77
4-2-9 Sb首要析出相區 84
4-2-10 三元Ge-Co-Sb系統液相線投影圖總結 86
4-3 Sn-Co-Sb三元系統液相線投影圖 87
4-3-1 CoSb首要析出相區 92
4-3-2Co3Sn2首要析出相區 103
4-3-3CoSn首要析出相區 105
4-3-4CoSbSn2首要析出相區 106
4-3-5 CoSb2首要析出相區 107
CoSn2首要析出相區 111
4-3-7 三元Sn-Co-Sb系統液相線投影圖總結 112
4-4四元Ge-Sn-Co-Sb系統之熱電性質 113
4-4-1 CoSb3合金製程比較 113
4-4-2 二元CoSb3合金熱電性質探討 118
4-4-3四元Ge-Sn-Co-Sb合金熱電性質探討 121
五、結論 152
七、參考文獻 155

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