Ni 障層與Ag2Te、(Bi,Sb)2Te3、Bi2(Te,Se)3熱電基材間之界面反應

Interfacial reactions between Ni barrier layer and thermoelectric substrates: Ag2Te, (Bi,Sb)2Te3, and Bi2(Te,Se)3

楊庭瑞(Ting-ruei Yang)

指導教授 ： 陳信文

國立清華大學/工學院/化學工程學系/碩士(2015年)

https://doi.org/10.6843/NTHU.2015.00065

摘要

熱電元件可以將熱能轉換成電能，在能源短缺的今日受到廣泛重視。熱電元件中一般存在著許多之銲點。為了避免銲料合金與熱電基材之直接反應，通常會使用阻障層將其隔開。Ni是常見的阻障層，探討Ni與熱電基材間之界面反應，對熱電元件的可靠度評估十分重要。本研究探討Ni阻障層與Ag2Te、(Bi,Sb)2Te3、Bi2(Te,Se)3等三種常見熱電基材間之界面反應。秤取適量之純元素，熔融、均勻混合後淬冷、回火，以製備Ag2Te、(Bi,Sb)2Te3、Bi2(Te,Se)3熱電基材。再以電鍍方式在熱電材料表面上鍍Ni，所鍍的Ni層厚度約為60μm。
Ni/Te在200oC反應720小時，界面生成Ni3Te2、NiTe0.775以及NiTe2相，反應層厚度約為15.5μm。Ni/Ag2Te在200oC反應720小時，在界面生成了二個不同之反應區域。在靠近Ni端，生成了一層純銀層，而在靠近Ag2Te端，則生成了二相混雜的手指型反應層。其中深灰色相應為Ni3Te2相之外，而白色相可能為溶入Ni的Ag2Te 相，反應層厚度則為8.1μm。Ni/Te以及 Ni/Ag2Te在250oC下的界面反應。Ni/Te界面處同樣生成了Ni3Te2、NiTe0.775以及NiTe2相，反應720小時，反應層厚度約為102.4μm。Ni/Ag2Te在250oC反應720小時，在界面生成了二個不同之反應區域。在靠近Ni端，生成了一層純銀層，與200oC之結果有所差異的是，在靠近Ag2Te端生成為連續的Ni3Te2反應層
本研究探討了Ni阻障層對p型(Bi0.25Sb0.75)2Te3及n型Bi2(Te0.9Se0.1)3熱電材料在300℃的界面反應。發現在Ni/(Bi0.25Sb0.75)2Te3固/固反應中，生成深灰色相，經組成分析研判可能為Sb-Ni-Te三元相或NiTe2相溶有Sb，同時也發現了白色(Bi,Sb)2Te3¬¬¬¬相的生成，而在310小時的反應偶後，皆發現在白色(Bi,Sb)2Te3¬¬¬¬相區內有條狀未知相生成。在Ni/Bi2(Te0.9Se0.1) 固/固反應中則生成一深灰色相，經組成分析研判可能為一Bi-Ni-Te三元相亦或是NiTe2相溶有Bi，同時也發現了亮白色BiTe相以及灰色不連續之條狀相散布在白色BiTe相中。在250℃以及300℃皆可觀察到，在相同反應時間下，Ni/Bi2(Te0.9Se0.1)反應偶所生成的反應層厚度明顯比Ni/(Bi0.25Sb0.75)2Te3所生成的反應層厚度來的厚。此外，此兩組300 oC反應偶與250 oC反應偶進行比較，在相同反應時間下，高溫下反應偶其反應層厚度明顯比低溫的反應偶來的厚，顯示此兩組反應偶，其反應層成長速率與其反應溫度有正相關。

關鍵字

界面反應 ； 熱電 ； 阻障層

並列摘要

Thermoelectric devices can convert heat into electricity directly, and have attracted enormous research interests. There are usually numerous solder (or braze) joints in thermoelectric devices. To prevent direct contact and interfacial reactions between solder (or braze) and thermoelectric materials, barrier layer is often used. Ni is the most commonly used barrier layer material. Examination of the interfacial reactions between Ni and thermoelectric substrates is fundamentally important for reliability assessment of the thermoelectric devices. This study investigates interfacial reactions between Ni and three kinds of thermoelectric materials: Ag2Te, (Bi,Sb)2Te3, and Bi2(Te,Se)3. The thermoelectric substrates are prepared with proper amounts of pure constituent elements, and are then plated with Ni. The thickness of Ni layer is 60μm.
Ni3Te2, NiTe0.775 and NiTe2 are formed in the Ni/Te couple reacted at 200oC for 720 hours. Two reaction regions are observed in the Ni/Ag2Te couple reacted at 200oC for 720 hours. A continuous Ag layer is formed adjacent to the Ni substrate. The other reaction region is a two-phase finger-type mixture. The darker phase in this two-phase region is the Ni3Te2 phase and the other brighter phase is Ag2Te phase with Ni solubility. This study also investigates the interfacial reactions between Ni/Te couple and Ag2Te couple at 250 oC. Ni3Te2, NiTe0.775 and NiTe2 are also formed in the Ni/Te couple reacted at 250oC for 720 hours, and the thickness of reaction layer is about 102.6μm. Two reaction regions are observed in the Ni/Ag2Te couple reacted at 250oC for 720 hours. A continuous Ag layer is formed adjacent to the Ni substrate. Comparing with those in the Ni/Ag2Te 200oC reaction couple, a continuous Ni3Te2 reaction layer is formed adjacent to the Ag2Te substrate.
The interfacial reactions between the Ni barrier layer and the P-type (Bi1-xSbx)2Te3 and n-type Bi2(Te1-ySey)3 thermoelectric materials at 300oC are examined. Two reaction phase layers are observed in the Ni/(Bi0.25Sb0.75)2Te3 couples reacted at 300oC. The phase layer adjacent to the Ni substrate is likely a Sb-Ni-Te ternary compound or the Ni3Te2 phase with significant Sb solubility.In the In the Ni/ Bi2(Te0.9Se0.1)3 couple reacted at 300oC two reaction phase layers are also found. The BiTe phase is adjacent to the Bi2(Te0.9Se0.1) substrate, while a Bi-Ni-Te ternary compound or the NiTe2 phase with Bi solubility is formed adjacent to the Ni substrate. It can be found that the thickness of the reaction layers in the Ni/Bi2(Te0.9Se0.1)3 couple is thicker than that in the Ni/(Bi0.25Sb0.75)2Te3. Furthermore, the reaction rate at 300oC is faster than that at 250oC.

並列關鍵字

Interfacial reaction ； Thermoelectric ； Diffusion barrier

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