Interfacial reactions between pure Cu, Ni, and Ni–Cu alloys and p-type Bi2Te3 bulk thermoelectric material

Autor: Hiroyuki Shibata, Shigeru Suzuki, Masanori Tashiro, Kozo Shinoda, Tsuyoshi Kajitani, Koichi Ikemoto, Sohei Sukenaga
Rok vydání: 2021
Předmět:
Zdroj: Journal of Materials Science. 56:16545-16557
ISSN: 1573-4803
0022-2461
Popis: Bismuth telluride (BT) displays one of the highest thermoelectric performances between ambient temperature and 473 K. In general, although a thermoelectric material is connected to a metal electrode through soldering when thermoelectric modules are assembled, the solder components diffuse into the thermoelectric element at operating temperatures and under current stress. It is widely known that p-type bismuth telluride (p-BT) with a composition similar to that of Bi0.5Sb1.5Te3 includes a pure Te phase when the material is made using a melt growth process. Because the eutectic temperature of the pseudo-binary Bi0.5Sb1.5Te3–Te system is close to 693 K, a Te-rich liquid should be produced from p-BT at elevated temperatures above the eutectic point. It is possible for the produced liquid to be utilized as a flux to allow direct bonding between the metallic electrode material and p-BT without using solder. In this study, the reactivity between p-BT and selected metallic substrates (Cu, Ni, or 99.7 Ni–0.3 Cu (at.%)) was investigated at 773 K in an argon atmosphere, as a fundamental study of the joining process. Cu is strongly reactive to p-BT, whereas Ni has a modest reactivity against p-BT. Furthermore, the addition of a small amount of Cu to Ni drastically enhanced the diffusivity of Te in the Ni substrate. Our findings suggest that Cu addition plays a key role in controlling the reactivity, which is directly linked to the bonding strength, interfacial resistivity, and thermal stability.
Databáze: OpenAIRE
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