Improvement of Contact and Bonding Performance of Mg 2 Si/Mg 2 SiNi 3 Thermoelectric Joints by Optimizing the Concentration Gradient of Mg

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.