Enhancing Interfacial Properties of Mg₂Si-Based Thermoelectric Joint with Mg₂SiNi₃ Compound as Electrodes

The phase component and its evolution during aging at the joint between thermoelectric (TE) materials and electrodes are of much importance to the quality and the performance of the TE devices. While the figure of merit zT of TE materials determines the maximum efficiency of TE devices, undesired side reactions causing the growing interfacial resistance or mechanical failures between TEs and metal electrodes limit the actual performance of devices. Herein, the candidate electrode materials (Mg₂Ni and Mg₂SiNi₃) for Mg₂Si are explored, which is one of the cost-effective and environmentally friendly TE materials exhibiting high zT. The electrodes are directly bonded to Mg₂Si by field-activated pressure-Assisted sintering (FAPAS) in one-step process. The interfaces of fabricated joints with different sintering times are monitored by electron microscopy, followed by the measurement of shear strength and the contact resistances. Outperforming strength (28.29 MPa) and contact resistance (63 μΩ cm²) are observed with Mg₂SiNi₃ at the joint bonded for 30 min. A long-term stability test on Mg₂SiNi₃/Mg₂Si joint reveals a minute increase in the contact resistance as well as sufficient mechanical stability, suggesting that Mg₂SiNi₃ is a great candidate of the electrode materials for Mg₂Si.