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

Masanori Tashiro, Sohei Sukenaga, Koichi Ikemoto, Kozo Shinoda, Tsuyoshi Kajitani, Shigeru Suzuki, Hiroyuki Shibata

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


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. Graphical abstract: [Figure not available: see fulltext.]

Original languageEnglish
Pages (from-to)16545-16557
Number of pages13
JournalJournal of Materials Science
Issue number29
Publication statusPublished - 2021 Oct


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