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

In order to improve the stability of Bi₂Te₃-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_0.4Sb_1.6Te₃ and Co/Bi₂Te_2.7Se_0.3. The results showed that the Co/Bi_0.4Sb_1.6Te₃ joint had diffusion thickness of 1.6 µm, contact resistivity of 0.83 µΩ cm², and bonding strength of 4.86 MPa for the barrier layer. Similarly, the Co/Bi₂Te_2.7Se_0.3 joint had diffusion thickness of 1.6 µm, contact resistivity of 0.75 µΩ cm², 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 Bi₂Te₃-based thermoelectric devices.