Interfacial reactions in Ni/CoSb_3 couples at 450 ºC

Abstract

CoSb_3-based alloys are promising thermoelectric materials, and nickel is commonly used as barrier layer. This study examines interfacial reactions in the Ni/Sb and Ni/CoSb_3 couples reacted at 723 K. Three reaction phases, Ni_5Sb_2, NiSb and NiSb_2, are found in the Ni/Sb couples. In the Ni/CoSb_3 couples, the reaction path is Ni/Ni_5Sb_2/(Co,Ni)Sb/CoSb_3. Nickel is the fastest diffusion species, and the growth front is at the (Co,Ni)Sb/CoSb_3 interface. Co is the second fastest diffusion species, and a Co-rich region is formed at the Ni phase. The reaction layers grow with longer reaction time. Their average growth rates in the Ni/Sb and Ni/CoSb_3 couples reacted for 20 h are 1.1 μm/h and 1.0 μm/h, respectively.

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