Mo-Fe/NbFeSb Thermoelectric Junctions: Anti-Thermal Aging Interface and Low Contact Resistivity.

In recent years, high-performance half-Heusler compounds have been developed as promising thermoelectric materials for power generation. Aiming at practical device applications, one key step is to seek suitable metal electrodes so that low interfacial resistivity is guaranteed under long-term thermal aging. In the previous work, the fresh Mo/Nb0.8Ti0.2FeSb junction was found exhibiting low contact resistivity below 1 μΩ cm2; however, it increased by tens of times under long-term thermal aging, mainly originating from the formation of the high-resistivity FeSb2 phase and the appearance of cracks. Here, the Mo-Fe electrodes are employed to build the junctions with Nb0.8Ti0.2FeSb. The interfacial behavior and contact resistance in these junctions were investigated both before and after the thermal aging. Interestingly, no obvious formation of FeSb2 phase and cracks were observed. As a result, the contact resistivity was below ∼1 μΩ cm2 after 15 days' thermal aging, indicating better connection reliability and lower contact resistivity compared to the Mo/Nb0.8Ti0.2FeSb junction. These findings highlight the applicability of Mo-Fe electrodes and pave the way for NbFeSb-based half-Heusler thermoelectric materials for device applications.