Study on the Preparation and Properties of a Co-Based Barrier Layer by Diffusion Welding

In order to improve the stability of Bi 2 Te 3 -based thermoelectric devices, we attempted to prepare a barrier layer via diffusion welding using Co powder as the barrier materials. The diffusion welding process was conducted at 674 K for a duration of 5 min. The optimal connection was achieved at the interfaces of Co/Bi 0.4 Sb 1.6 Te 3 and Co/Bi 2 Te 2.7 Se 0.3 . The results showed that the Co/Bi 0.4 Sb 1.6 Te 3 joint had diffusion thickness of 1.6 µm, contact resistivity of 0.83 µΩ cm 2 , and bonding strength of 4.86 MPa for the barrier layer. Similarly, the Co/Bi 2 Te 2.7 Se 0.3 joint had diffusion thickness of 1.6 µm, contact resistivity of 0.75 µΩ cm 2 , and bonding strength of 3.99 MPa for the barrier layer. The thermoelectric device fabricated through this process exhibited a hot–cold cycle number of 35,000, which was significantly higher than the device with a Ni-based barrier layer under similar experimental conditions. Thus, it indicates that Co is a promising material for the preparation of barrier layers in Bi 2 Te 3 -based thermoelectric devices.