Enhanced Contact Performance and Thermal Tolerance of Ni/Bi₂Te₃ Joints for Bi₂Te₃-Based Thermoelectric Devices

Ni metal has been widely used as a barrier layer in Bi₂Te₃-based thermoelectric devices, which establishes stable joints to link Bi₂Te₃-based legs and electrodes. However, the Ni/Bi₂Te₃ joints become very fragile when the devices were exposed to high temperature, causing severe performance deterioration and even device failure. Herein, stable Ni/Bi₂Te₃ joints have been established by arc spraying of the Ni barrier layer on the Bi₂Te₃-based alloys. The interface microstructure and contact performance including the bonding strength and contact resistivity of the arc-sprayed Ni/Bi₂Te₃ joints are investigated. The results indicate that, as compared with traditional Ni/Bi₂Te₃ joints, the arc-sprayed Ni/Bi₂Te₃ joints have comparably low contact resistivity while possessing a 50% higher bonding strength. Aging the joints as an exposure to high-temperature circumstances, the arc-sprayed Ni/Bi₂Te₃ joints exhibit much better tolerance to the thermal shock with stable bonding strength and contact resistivity. The enhanced interfacial contact performance and thermal tolerance should be attributed to the thick Ni barrier layer and interface reaction layer with good Ohmic contact. This work provides an effective strategy to establish stable joints for the Bi₂Te₃-based thermoelectric devices with improved thermal stability.