Low interfacial resistivity in CoSi2/ZrCoSb thermoelectric junctions

Both p-type and n-type MCoSb (M = Ti, Zr, Hf) half-Heusler compounds have been found to exhibit high thermoelectric performance for power generation, but there is still a lack of research on the suitable interfacial materials to connect both p-type and n-type MCoSb for device assembly. Here, CoSi2 was selected as the electrode to connect p-type Hf0.5Zr0.5CoSb0.8Sn0.2 and n-type (Hf0.6Zr0.4)0.88Nb0.12CoSb, and the interfacial microstructure and interfacial contact resistivity were studied before and after thermal aging. In both types of thermoelectric junctions, the interface layer with a thickness from several to tens of μm is formed, which ensures a good bonding strength. The interfacial contact resistivity of both as-sintered thermoelectric junctions was less than 1 μΩ cm2, which rises to 3–4 μΩ cm2 after aging for 8 days at 1,073 K and keeps almost unchanged during the longer aging treatment. The present work demonstrates that CoSi2 is a suitable electrode material for both p- and n-type MCoSb due to the good bonding strength and the low interfacial resistivity, which paves the way for the applications of MCoSb-based TE materials.