臺灣博碩士論文加值系統

能源危機是全世界共同問題，研究能源替代及增加材料使用效率，皆是現在能源發展之方向。而熱電材料是個固態轉換器，能將電能和熱能互相轉換，且具有體積小、壽命長、無運動組件等優點，因此在能源研究上受到很大的關注及討論。GeTe為常見且被認為具有潛力的中溫型熱電材料，在720K時zT值高達0.8，此時其為立方結構，不具方向性問題。而GeTe的電阻率非常低，但具有較高的熱傳導率，所以可藉由摻雜(doping)來提升其熱電性質。相圖提供基礎且重要的資訊，探討材料相轉變及內部結構變化之重要資訊。對熱電材料而言，結構與性質十分相關，因此必須以相圖為基礎來研究熱電材料。Ge-Te-In三元系統相圖為Ge-Te-In熱電系統之重要基礎。因此本研究主要以實驗與分析來建立其三元系統，並依據相圖找出GeTe穩定存在之相區，進行熱電性質的量測。本研究的工作將包括: (1)以實驗測定Ge-Te-In三元系統之液相線投影圖、(2)以實驗測定Ge-Te-In三元系統的350OC等溫橫截面圖 (3)量測In摻雜GeTe之熱電性質。在本研究所配置之In摻雜GeTe合金中，合金#8 (In2Te3)0.025(GeTe)2.925在623K時具有最高的zT值高達1.12，與未參雜之GeTe相比上升了150%。進一步利用穿透式顯微鏡(TEM)觀察到合金內具有奈米級雙晶(twin)結構，且此twin的結構會同時降低熱傳導係數及增加電導率，故使zT值提升。

Thermoelectric (TE) materials, which can convert waste heat into precious electricity, has been viewed as an effective solution for the worldwide energy issue. The simple cubic GeTe is known as a promising mid-temperature TE material, mainly owing to its excellent power factor. Minor doping might be effective in reducing the thermal conductivity of GeTe and thus enhancing the figure-of-merit (zT). Phase diagram, which provides basic yet essential information, probes the phase stability and thermodynamic behavior of complicated materials systems. With an aid of phase diagram and microstructural evolution, the TE properties can be optimized systematically. This study aims to determine the ternary phase diagrams of Ge-Te-In system, and the efforts include: (1) determining the liquidus projection by water-quenched alloys, (2) constructing the 350˚C isothermal section by thermally-equilibrated alloys, and (3) measuring the thermoelectric property of In-doped GeTe alloys. In this work, alloy (In2Te3)0.025(GeTe)2.925 reaches the highest peak value of zT~1.12 at 623K, showing 150% enhancement compared with that of the undoped GeTe (zT~0.75). On the basis of TEM analysis, the nano-sized twinning structure was discovered throughout the (In2Te3)0.025(GeTe)2.925, which leading to the reduced thermal conductivity and enhanced electrical conductivity.

摘要 ................................................................................................................. i
Abstract.......................................................................................................... ii
目錄 ............................................................................................................... iii
圖目錄 ............................................................................................................ v
表目錄 .......................................................................................................... xii
一、前言 ........................................................................................................ 1
二、文獻回顧 ................................................................................................. 8
2.1相圖 ....................................................................................................... 8
2.1-1 Ge-Te二元系統相平衡圖 .............................................................. 8
2.1-2 In-Te二元系統相平衡圖 ............................................................... 8
2.1-3 Ge-In二元系統相平衡圖 .............................................................. 9
2.1-4 Ge-In-Te三元系統計算液相投影圖 ........................................... 10
2.2 熱電材料 ............................................................................................ 10
2.2-1 GeTe熱電材料 ............................................................................ 11
三、研究方法 ............................................................................................... 21
3.1 Ge-Te-In三元系統相平衡 ................................................................. 21
3.1-1 合金製備 ..................................................................................... 21
3.1-2 相平衡實驗及分析 ...................................................................... 21
3.2 Ge-Te-In三元系統液相線投影圖 ...................................................... 22
3.2-1液相線投影圖合金製備 ............................................................... 22
3.2-2液相線投影圖合金分析 ............................................................... 23
3.3 熱電性質 ............................................................................................ 23
四.結果與討論 .............................................................................................. 26
4.1 三元系統液相線投影圖 ..................................................................... 26
4.1-1 首要析出相：GeInTe3 ................................................................ 33
4.1-2 首要析出相：Ge2In3Te15 ............................................................ 40
4.1-3 首要析出相：Ge ......................................................................... 42
4.1-4 首要析出相：GeTe ..................................................................... 51
4.1-5 首要析出相：Te ......................................................................... 53
4.1-6 首要析出相：In2Te5 ................................................................... 58
4.1-7 首要析出相：In2Te3+x................................................................. 62
4.1-8 首要析出相：InTe ...................................................................... 65
4.1-9 首要析出相：In4Te3 ................................................................... 69
4.2 350oC Ge-Te-In三元系統等溫橫截面 ............................................... 73
4.2-1 GeInTe3 單相區 .......................................................................... 81
4.2-2 L+ In4Te3兩相區 ......................................................................... 83
4.2-3 Ge+ In4Te3兩相區 ....................................................................... 86
4.2-4 Ge+ InTe兩相區 ......................................................................... 89
4.2-5 GeInTe3+ In2Te3+X兩相區 ........................................................... 92
4.2-6 GeInTe3+ In2Te5兩相區 .............................................................. 94
4.2-7 GeInTe3+ Te兩相區 .................................................................... 97
4.2-8 GeInTe3+In3Te4兩相區 ............................................................... 98
4.2-9 Ge+GeTe兩相區 ......................................................................... 99
4.2-10 GeTe+GeInTe3兩相區 ............................................................. 100
4.2-11 GeTe+ GeTeIn3+ In3Te4三相區 .............................................. 102
4.2-12 Ge+ GeTe+ In3Te4三相區 ....................................................... 108
4.2-13 GeTe+Te+ GeInTe3三相區 ..................................................... 111
4.2-14 In2Te5+Te+ GeInTe3三相區 .................................................... 115
4.2-15 In2Te5+In2Te3+x+ GeInTe3三相區 ........................................... 117
4.3 熱電性質 .......................................................................................... 120
4.3-1 GeTe之熱電性質....................................................................... 123
4.3-2 (GeTe)1-xInx之熱電性質 ............................................................ 123
4.3-3 GeTe摻雜In之熱電性質 ......................................................... 128
4.3-4 GeTe沿著In2Te3之熱電性質 ................................................... 133
4.3-5 合金#8 (In2Te3)0.025(GeTe)2.925 之TEM金相分析 ................... 137
4.3-6熱電性質之總結 ......................................................................... 140
五、結論 .................................................................................................... 147
5.1相圖 ................................................................................................... 147
5.2 熱電性質 .......................................................................................... 148
六、參考文獻 ............................................................................................. 152

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