能源轉換的過程中，逸散到大氣的熱能若能被回收再利用可以有效的提高有限能源的使用率。而熱電材料由於其能夠將熱能與電能直接轉換，因此造成前仆後繼的研究與探討。然而其模組中的接點問題一直是穩定性的一大隱憂，合適的阻障層可以延長其使用的壽命，因此若能了解阻障層與熱電材料之間的界面反應，便可透過擴散的機制來設計出合適的阻障層。透過相關元素的相平衡研究可以更快釐清其元素交互作用的熱力學性質。
SnSe2以及Pb1-xSnxSe是具潛力的熱電材料，Ni和Co是常用的阻障層。本研究將探討Ni和Co阻障層與SnSe2以及Pb1-xSnxSe之界面反應，並了解其界面成長機制，與相關的相平衡研究。本研究利用電鍍的方式將阻障層鍍於基材上。隨後將反應偶試樣真空封入石英管後，放入500℃、300℃以及200℃的高溫爐中進行界面反應，而相平衡實驗則是以些許合金點配製並平衡多個月的結果。
研究結果顯示阻障層(Ni)與熱電材料(SnSe2)反應偶在500℃的反應溫度下會生成三層界面反應層分別為三相(Ni5.62SnSe2+NiSe+Ni3Sn2)、兩相(Ni3Sn2+NiSe)以及兩相(NiSe+SnSe)。而300℃系統的結果較500℃系統多了一層反應層，其反應的生成相為三相(Ni5.62SnSe2+NiSe+Ni3Sn2)、兩相(Ni3Sn2+NiSe)、兩相(NiSnSe+NiSe)以及兩相(NiSe+SnSe)。而200℃的反應也有相似的結果，但其中的最後一層界面反應層認為是Ni-26at%Sn-50at%Se介金屬化合物。
因SnSe2的特殊結構使得SnSe2¬相變為SnSe時會整層材料相變，因此在反應偶下側可以發現相變後具有不規則孔洞結構的SnSe。其相轉變機制為(SnSe2→SnSe+Se(liquid))。因Se元素的蒸氣壓大，Se(liquid)容易產生氣相的Se(gas)，氣相的Se(gas)再與Ni反應為NiSe相。
在500℃ Co/SnSe2的系統中，界面處的生成相為CoSe與SnSe。然而在300℃與200℃系統中，界面處的兩層反應層分別為兩相(CoSe+SnSe)以及SnSe。在高溫系統中(500℃)SnSe的形貌含有不規則的孔洞，然而在低溫系統中(300℃與200℃)，因Co+Se→CoSe的反應速率下降，生成的SnSe則沒有孔洞。
500℃ (Co,Ni)/SnSe2系統中，擴散速率Ni>Se>Co，其生成相分別為(Co,Ni)3Se2、兩相((Co,Ni)Se+Ni3Sn2)、兩相(NiSe+SnSe)。而200℃ 的(Co,Ni)/SnSe2反應偶有些許的不同，最靠近SnSe2的生成相為Ni-26at%Sn-50at%Se介金屬化合物，其擴散路徑為(Co,Ni)/ Ni3Sn2/(Co,Ni)Se/SnSe/(Ni-26at%Sn-50%Se)介金屬/SnSe2。
阻障層(Ni)與熱電材料(Pb1-xSnxSe)反應偶在500℃反應下，有兩層界面反應層，其生成相為兩相(Ni5.62SnSe2+ Ni¬3Pb2Se2)以及三相(Ni5.62SnSe2+Pb1-xSnxSe+Ni-Sn compound)，而第二層中Pb1-xSnxSe在反應後的Sn含量會有遞減的情形發生。在阻障層(Co)與熱電材料(Pb1-xSnxSe)的反應偶中沒有發現有界面生成相，因此(Co,Ni)系統中也只有Ni進行反應，故其擴散路徑與Ni系統相同。

In the energy conversion process, if the heat energy leaked into the atmosphere can be recycled, the utilization rate of the energy can be improved. Thermoelectric materials can directly convert the heat into electrical energy, so it has attracted widespread attention. However, the contact problem in the module has always been a major concern for the stability. A suitable barrier layer can extend its lifespan. Therefore, if the interfacial reaction between the barrier layer and the thermoelectric material can be well understood, a suitable barrier layer can be designed. Furthermore, phase equilibrium is an useful information for understanding the thermodynamic properties of all the elements.
SnSe2 and Pb1-xSnxSe are potential thermoelectric materials, and Ni and Co are commonly used to be the barrier layers. This research aims to understand the interface diffusion mechanism between barrier layers (NiandCo) and thermoelectric materials (SnSe2 and Pb1-xSnxSe). In this experiment, Nickel and Cobalt are electroplated on the SnSe2 and Pb1-xSnxSe. The reaction couple is vacuum sealed in a quartz tube and placed in a high-temperature furnace set as 500°C and 300°C. The isothermal phase diagram of Ni-Sn-Se at 500°C and 300°C are determined by the homogeneous sample annealed for several months.
The results show that the Ni/SnSe2 couple at 500°C form the three reaction layers which are Ni5.62SnSe2+NiSe+Ni3Sn2(three phases), Ni3Sn2+NiSe(two phases), and NiSe+SnSe(two phases), respectively. The result of the 300°C system has one more reaction layer than that of the 500°C system. Ni/SnSe2 couple at 200°C also has similar results, but the reaction layer closed to SnSe2 is considered to be a Ni-26at%Sn-50at%Se intermetallic compound.
Due to the anisotropic property of SnSe2, the entire layer of material will undergo a phase change when SnSe2 is transformed into SnSe. Therefore, SnSe with the irregular pores can be found on the lower side of the reaction couple. Thus, the phase transition mechanism is (SnSe2→SnSe+Se(liquid)). Due to the high vapor pressure of the Se element, Se (liquid) tends to produce Se (gas). The Se(gas) will easily react with Ni to form the NiSe phase.
In the 500°C Co/SnSe2 system, the formation phases at the interface are CoSe and SnSe. However, in 300°C and 200°C systems, the two reaction layers at the interface are CoSe+SnSe(two phases)and SnSe. The morphology of SnSe in the high temperature system (500°C) contains irregular pores, but in the low temperature system (300°C and 200°C), the SnSe has no pores due to the lower reaction rate of Co+Se→CoSe. In the 500℃ (Co,Ni)/SnSe2 system, the diffusion rate is considered as Ni>Se>Co. The formation phases are (Co,Ni)3Se2, (Co,Ni)Se+Ni3Sn2(two pahses), NiSe+SnSe(two-phase). The (Co,Ni)/SnSe2 reaction at 200℃ is occasionally slightly different. The reaction layers closed to SnSe2 is Ni-26at%Sn-50at%Se intermetallic compound. Its diffusion path is (Co,Ni)/Ni3Sn2/(Co,Ni)Se/SnSe/(Ni-26at%Sn-50%Se)intermetallic compound/SnSe2.
The Ni/Pb1-xSnxSe at 500℃ has two interfacial reaction layers. The formation phases are Ni5.62SnSe2+Ni3Pb2Se2 (two phases) and Ni5.62SnSe2 +Pb1-xSnxSe+Ni-Sn compound (three phases). The Sn content of Pb1-xSnxSe in the second reaction layer will be lower in the left part than in the right part after the reaction. Furthermore, no interfacial reaction was found in the Co/Pb1-xSnxSe. Therefore, in the (Co, Ni) system only Ni is reactive.

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