- 學位論文
PbSe,SnSe,SexTe1-x,SnTe,和SnTe1-xSex熱電材料與鎳擴散阻障層之界面反應與其相關相圖
Interfacial reactions between Ni barrier layer and thermoelectric PbSe, SnSe, SexTe1-x, SnTe, and SnTe1-xSex alloys and their related phase diagrams
摘要
因為在提高能源使用效率與再生能源開發二大重要能源議題上的重要性，熱電材料吸引了全世界的關注。熱電模組通常由P-N接面的陣列組成，當中也因此存在著許多接點。PbSe和包含SnSe與SnTe的Se‒Sn‒Te系統的熱電材料，是極具潛力的熱電材料。Ni常作為阻障層，以避免熱電基材和銲料間的顯著反應。因為Ni阻障層與熱電基材直接相接， 因此關於Ni層與熱電基材間的界面反應的了解，對熱電模組的開發以及可靠度評估將十分重要。相圖提供相平衡資訊。相圖除了是材料的重要基礎知識外，也是探討界面反應非常有用的工具。本研究評估文獻中的相關組成系統的相圖與相平衡資料，提出了相關材料系統的等溫恆截面相圖。本研究系統性的探討了Ni/PbSe, Ni/SnSe, Ni/SexTe1-x (x=0.1, and 0.2), Ni/SnTe, 與Ni/SnTe0.9Se0.1 反應偶的界面反應。熱電基材是由組成的純物質製備，然後以電鍍方法鍍上Ni層。製備好的反應偶封於抽真空的石英管中，再經不同時間的熱處理。以實驗量測反應偶中的反應生成相，並配合相關材料系統相圖，以解釋與了解其反應路徑。在300℃, 350℃ 及 400℃的Ni/PbSe反應偶中生成了Ni3Pb2Se2相，但是在250℃則無明顯界面反應。 Ni/PbSe 的反應路徑為Ni/Ni3Pb2Se2/PbSe 。Ni/SnSe在250℃ 及 300℃的反應路徑為Ni/Ni3Sn/Ni3Sn2/NiSe/Ni5.62SnSe2/Ni3SnSe/ NiSnSe/SnSe。NiSnSe 及 Ni3SnSe是首次發現的三元相，它們是因Ni快速擴散所生的界穩相。Ni/SexTe1-x在200℃的反應路徑為Ni/Ni3Te2/NiTe2/SexTe1-x。Ni/SnTe 在400℃的反應路徑為Ni/Ni3Sn/Ni3Sn2/Ni5.78SnTe2/Ni3SnTe2/SnTe。Ni/SnTe0.9Se0.1 在400℃的反應路徑與Ni/SnTe的反應路徑相似。界面反應速率隨溫度降低而減小，反應層厚度隨著反應時間拉長而增厚。從反應偶的微結構與相生成順序，推知Ni是上述這些反應偶中擴散最快的元素。
並列摘要
Thermoelectric (TE) materials have attracted worldwide attention because of their importance in enhancing energy usage efficiency and developing reliable renewable energy sources which are considered the two pillars of sustainable energy. Thermoelectric modules are usually made with arrays of P-N junctions, and there are various joints in thermoelectric modules. PbSe compound and Se‒Sn‒Te-based materials including SnSe and SnTe compounds are among the most promising thermoelectric materials. Ni is usually used as a barrier layer to prevent significant interfacial reactions between joining materials and thermoelectric substrates. Since Ni barrier layer is in direct contact with thermoelectric substrates, knowledge of interfacial reactions between Ni barrier layer and thermoelectric materials is thus fundamentally important for development and reliability assessment of thermoelectric modules. Phase diagrams provide phase equilibria information. Besides they are important basic knowledge, they are very useful in the illustrations of interfacial reactions. Phase diagrams of related materials systems are proposed in this study based on the phase diagrams of their constituent systems and related phase equilibria results in the literatures. This study systematically examines the interfacial reactions in Ni/PbSe, Ni/SnSe, Ni/SexTe1-x (x=0.1, and 0.2), Ni/SnTe, and Ni/SnTe0.9Se0.1 couples. The thermoelectric substrates are prepared with pure constituent elements and electroplated with Ni layer. The couples were encapsulated in vacuumed quartz tubes and heat-treated for various lengths of time. The reaction phases are experimentally determined. The reaction paths are illustrated based on the reaction phases and the proposed phase diagrams. One reaction phase, Ni3Pb2Se2, is formed in the Ni/PbSe couples reacted at 300℃, 350℃ and 400℃, but no interfacial reaction at 250℃. The reaction path is Ni/Ni3Pb2Se2/PbSe in the Ni/PbSe couples. The reaction paths in the Ni/SnSe couple reacted at 250℃ and 300℃, are both Ni/Ni3Sn/Ni3Sn2/NiSe/Ni5.62SnSe2/Ni3SnSe/NiSnSe/SnSe. Both NiSnSe and Ni3SnSe are ternary phases observed for the first time. They are metastable phases formed by rapid diffusion of Ni into the SnSe substrate. The reaction path in the Ni/SexTe1-x couple reacted at 200℃ is Ni/Ni3Te2/NiTe2/ SexTe1-x and in the Ni/SnTe couple reacted at 400℃, is Ni/ Ni3Sn/Ni3Sn2/Ni5.78SnTe2/Ni3SnTe2/SnTe. In the Ni/SnTe0.9Se0.1 couple reacted at 400℃, the reaction path is the same as that of Ni/SnTe. The reaction rates decrease with lower reaction temperatures, and the reaction zone grows thicker with longer reaction time. Based on the microstructure analysis and the reaction phase sequences, it is concluded that Ni is the fastest diffusion species in all these couples.