能源是目前人類永續所面臨最嚴重之挑戰，但是目前能源的使用效率並不高，超過一半以上之能源是以廢熱方式逸散。熱電材料具有將熱與電能相互轉換的特色，具有很大的潛力可以應用於廢熱回收。廢熱的回收不僅可以提高能源的使用效率，同時也降低環境的汙染。由於廢熱回收的應用溫度較高，元件中的界面反應也會較嚴重，因此瞭解接點的界面反應是一個相當重要的議題。本研究所用之銲料合金為Ag-24.5at%Ge、障層材料為Ni或Co、熱電材料為PbTe，因此接點為Ag-24.5at%Ge/Ni(or Co)/PbTe，本研究探討此接點之界面反應。由於Ag-Ge-Ni和Ag-Ge-Co兩個三元系統的相平衡資訊缺乏，本研究探討相關材料系統(Ag-Ge-Ni與Ag-Ge-Co)的相圖，以實驗方式建構Ag-Ge-Ni在400oC和Ag-Ge-Co在750oC之等溫橫截面圖，並搭配CALPHAD計算相圖方式確認各相平衡關係。
本研究探討阻障層與銲料的界面反應，Ni/Ag-24.5at.%Ge於400oC反應中，界面生成較為鬆散的-Ni5Ge3相，靠近界面端的銲料因為Ge的反應消耗以及在固態的擴散較為緩慢，銲料會剩下不參與反應的Ag；Ni/Ag-24.5at.%Ge於750oC反應中，界面生成較為緻密的-Ni5Ge3相，由於銲料在熔融狀態比在固態的原子擴散速率會快上許多，因此靠近界面端的銲料沒有剩下不參與反應的元素。另外，本研究亦探討不同的阻障層對於界面反應的影響，Co/Ag-24.5at.%Ge於400oC和750oC的反應中，皆於界面生成-Co5Ge3相和CoGe相，但由於銲料於固態和液態的擴散速率不同，造成銲料在界面的差異以及反應路徑的不同。
本研究探討阻障層與熱電材料的界面反應，Ni/PbTe於400oC的反應中，界面並沒有生成任何介金屬相，結果顯示使用Ni作為阻障層，熱電元件應用於400oC的廢熱回收仍可維持接點的機械性質以及良好的熱電表現。

Finding a solution to energy-related problem is currently one of the greatest challenge faced by people. The power efficiency is low and approximately half of the energy is exhausted as waste heat. Thermoelectric device is regarded as a potential material for its ability of directly converting waste heat into electrical power. Thermoelectric materials are not only reducing the environmental pollution but also improving the power efficiency by recycling the waste heat. The operating temperature of devices in recycling waste heat is high, which may lead to form intermetallic compounds at interface that causes the reduction of thermoelectric performance and the decrease of reliability of the related products. The phase formation and phase transformation in the joints are crucial to the lifetime of products. Ag-24.5at.%Ge alloy is a promising Pb-free solder, Nickel and Cobalt are commonly used as barrier layer material, and lead-tellurium is one mid-temperature thermoelectric material. This study examines the interfacial reactions in the joint PbTe/Ni(or Co)/Ag-24.5at.%Ge, and proposes the phase diagrams of Ag-Ge-Ni and Ag-Ge-Co ternary system.
Interfacial reactions between diffusion barrier and solder are investigated. the -Ni5Ge3 phase is formed adjacent to the Ni substrate in the Ni/Ag-24.5at.%Ge couple reacted at 400oC. A region of nearly pure Ag is formed between this reaction phase and the eutectic Ag-24.5at%Ge, and is the result of Ag left over caused by the reactions between Ge and Ni. The -Ni5Ge3 phase is also formed in the Ni/Ag-24.5at.%Ge couple reacted at 750oC, but the microstructures of -Ni5Ge3 phase is different from those at 400oC, which is caused by the diffusion rate of solder in solid state and liquid state. In addition, Co/Ag-24.5at.%Ge couple reacted at 400oC and 750oC are examined as well. The -Co5Ge3 phase and CoGe phase form and grow with longer reaction time. Because diffusion rate of solder in solid state is higher than those in liquid state, it leads to different interfaces adjacent to the solder and reaction path. Phase diagrams including isothermal section of Ag-Ge-Ni ternary system at 400oC and Ag-Ge-Co ternary system at 750oC are experimentally established with CALPHAD.
Interfacial reactions between diffusion barrier and thermoelectric material are also investigated. No compound is observed in the Ni/PbTe couple reacted at 400oC, which means thermoelectric materials could maintain high thermoelectric performance. This results imply that Ni may be one of promising candidate of diffusion barrier for PbTe thermoelectric material recycling waste heat at 400oC.

摘要 i
Abstract ii
目錄 iii
表目錄 v
圖目錄 vi
一、前言 1
二、文獻回顧 6
2-1 Ag-Ge-Ni系統 6
2-1-1 Ag-Ge二元系統相平衡 6
2-1-2 Ag-Ni二元系統相平衡 6
2-1-3 Ge-Ni二元系統相平衡 7
2-1-4 Ag-Ge-Ni三元系統相平衡 7
2-2 Ag-Ge-Co系統 8
2-2-1 Ag-Co二元系統相平衡 8
2-2-2 Co-Ge二元系統相平衡 8
2-2-3 Ag-Ge-Co三元系統相平衡 8
2-3 Ni-Pb-Te系統 9
2-3-1 Pb-Te 二元系統相平衡 9
2-3-2 Pb-Ni 二元系統相平衡 9
2-3-3 Ni-Te 二元系統相平衡 9
2-3-4 Ni-Pb-Te三元系統相平衡 10
2-4 界面反應 23
2-4-1 Ag/Ni界面反應 26
2-4-2 Ge/Ni界面反應 26
2-4-3 Ni/Ag-Ge界面反應 27
2-4-4 Ag/Co界面反應 27
2-4-5 Ge/Co界面反應 27
2-4-6 Co/Ag-Ge界面反應 27
2-4-6 Ni/PbTe界面反應 28
三、研究方法 29
3-1 Ag-Ge-Ni 三元系統相平衡 29
3-2 Ag-Ge-Co三元系統相平衡 29
3-2 阻障層與銲料於750oC之固/液界面反應 30
3-3 阻障層與銲料於400oC之固/固界面反應 30
3-4 熱電材料與阻障層的界面反應 31
四、結果與討論 32
4-1 Ag-Ge-Ni 三元系統400oC等溫橫截面圖 32
4-1-1 Ge + Ag + NiGe 三相區 33
4-1-2 NiGe + Ag + Ni19Ge12 33
4-1-3 Ag-Ge-Ni三元系統400oC部分等溫橫截面圖結果 34
4-2 Ni/Ag-24.5at.%Ge於400oC之固/固界面反應 44
4-3 Ni/Ag-24.5at.%Ge於750oC之固/液界面反應 52
4-4 Ag-Ge-Co三元系統750oC 等溫橫截面圖 56
4-4-1 Ge + Liquid + CoGe2 三相區 57
4-4-2 CoGe2 + Liquid + Co5Ge7 三相區 57
4-4-3 Co5Ge7 + Liquid + CoGe 三相區 58
4-4-4 CoGe + Liquid + Ag 三相區 58
4-4-5 Ag-Ge-Co三元系統750oC部分等溫橫截面圖結果 59
4-5 Co/Ag-24.5at.%Ge於400oC之固/固界面反應 73
4-6 Co/Ag-24.5at.%Ge於750oC之固/液界面反應 83
4-7 Ni/PbTe於400oC之界面反應 91
五、結論 93
六、參考文獻 95

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