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 (Mg 2 Ni and Mg 2 SiNi 3 ) for Mg 2 Si are explored, which is one of the cost-effective and environmentally friendly TE materials exhibiting high zT . The electrodes are directly bonded to Mg 2 Si 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 cm 2 ) are observed with Mg 2 SiNi 3 at the joint bonded for 30 min. A long-term stability test on Mg 2 SiNi 3 /Mg 2 Si joint reveals a minute increase in the contact resistance as well as sufficient mechanical stability, suggesting that Mg 2 SiNi 3 is a great candidate of the electrode materials for Mg 2 Si.
Mg 2 SiNi 3, is a topologically densely packed intermetallic compound (TCP-IMC) and an excellent diffusion barrier material between nickel and Mg 2 Si-based thermoelectric material. However, even a little migration of the Mg atom from Mg 2 Si to Mg 2 SiNi 3 under the action of a driven force promotes the formation of an Mg deficiency region on the Mg 2 Si side, which destroys the balance of point defects and leads to performance deterioration. In this work, by adjusting the chemical potential of Mg across the Mg x Si 15 Ni 50 /Mg 2 Si ( x = 36, 50, 130) interface, the migration of Mg in thermoelectric material has been suppressed effectively. The results indicate that the contact performance and service stability of the Mg 130 Si 15 Ni 50 /Mg 2 Si interface has been improved by 50% compared to that of Mg 36 Si 15 Ni 50 /Mg 2 Si, which remains quite well after annealing at 400 ℃ for 480 h. TCP-IMC barrier with proper composition is a promising design for the manufacture of TEG interface to ensure its consistency in service especially under a large temperature difference.
危险品化学品经营许可证（带存储）