Study on the High Temperature Interfacial Stability of Ti/Mo/Yb0.3Co4Sb12 Thermoelectric Joints

Abstract

Abstract:To improve the interfacial stability at high temperatures, n-type skutterudite (SKD) thermoelectric joints with sandwich structures of Ti/Mo/Yb 0.3 Co 4 Sb 12 were successfully designed and fabricated. In this structure, Mo and Ti were introduced as the barrier layer with the goal of suppressing the interfacial diffusion and the buffer layer with the goal of enhancing the bonding strength, respectively. To evaluate the high temperature interfacial behavior of the Ti/Mo/Yb 0.3 Co 4 Sb 12 joints, thermal shocking between 0 • C and 600 • C and isothermal aging at a temperature range of 550 • C to 650 • C were carried out in vacuum. During the isothermal aging process, Ti penetrates across the Mo layer, and finally diffuses into the Yb 0.3 Co 4 Sb 12 matrix. By increasing the isothermal aging time, Ti continuously diffuses and reacts with the elements of Sb and Co in the matrix, consequently forming the multilayer-structured intermetallic compounds of Ti 3 Sb/Ti 2 Sb/TiCoSb. Diffusion kinetics was investigated and it was found that the interfacial evolution of the Ti/Mo/Yb 0.3 Co 4 Sb 12 joints was a diffusion-controlling process. During the diffusion process, the formed Mo-Ti buffer layer acts as a damper, which greatly decelerates the diffusion of Ti towards the Yb 0.3 Co 4 Sb 12 matrix at high temperatures. Meanwhile, it was found that the increase in the contact resistivity of the joints mainly derives from the inter-diffusion between Ti and Yb 0.3 Co4Sb 12 . As a result, the Ti/Mo/Yb 0.3 Co 4 Sb 12 joint demonstrates the excellent stability of the interfacial contact resistivity. Service life prediction was made based on the stability of the contact resistivity, and it was found that the Ti/Mo/Yb 0.3 Co 4 Sb 12 joint is qualified for practical applications at 550 • C.

Enhanced Interfacial Reliability and Mechanical Strength of CoSb3-Based Thermoelectric Joints with Rationally Designed Diffusion Barrier Materials of Ti-Based Alloys

“…The contact resistivity of the Ti−Ni/CoSb 3 joint after 16day aging is significantly greater than 10 μΩ•cm 2 (Figure 7b), indicating that the Ti−Ni/CoSb 3 TE joint will be failed after long-time working. As shown in Figure 7b, the contact resistivity of our Ti−Al−Si/CoSb 3 joint after 16-day aging at 500 °C (4.3 μΩ•cm 2 ) is lower and comparable with other reported CoSb 3 -based joints, such as the Ti/Mo/CoSb 3 joint aged at 550 °C for 50 days, 32 the Ti 94 Al 6 /CoSb 3 joint aged at 600 °C for 16 days, 33 the Fe 64 Ni 36 /CoSb 3 joint aged at 500 °C for 10 h, 23 the Co 60 Mo 40 /CoSb 3 joint aged at 550 °C for 100 h, 36 and the Ti 90 Mo 10 /CoSb 3 joint aged at 550 °C for 12 days. 28 As TE joints usually undergo a loading force and thermal stress during the service, high-performance TE joints also require high interfacial bonding strength of TE joints.…”

“…6,27,28 Therefore, the optimization of diffusion barrier materials is significant for CoSb 3 -based TE devices. As shown in previous reports, many metals and alloys have been used as diffusion barrier materials for CoSb 3 -based TE joints, such as Ti, 17,29−31 Ni, 31 Co, 31 Mo, 32 Nb, 18 Ti−Al alloys, 27,33 Al−Ni alloys, 34 TaN−Ta−TaN alloys, 35 Fe−Ni alloys, 23 Ti−Mo alloys, 28 and Co−Mo alloys. 36 Among these diffusion barrier materials shown above, Ti and Ti-based alloys have been demonstrated as good candidates for the diffusion barrier materials of CoSb 3 -based TE joints.…”

Expanding Plasma Process for Nitriding Mo–Ti Bilayer Thin Films

“…So, Mo-Ti alloys are formed. Such a result was obtained in a recent study on the formation of a Mo-Ti layer with a Ti content gradient, in Ti/Mo/Yb0.3Co4Sb12 thermoelectric joints heated at 550 °C in vacuum [23]. As also seen in Figure 3, the nitrogen and carbon signals are low in the as-deposited Ti-Mo bilayer.…”

Interaction of Skutterudites with Contact Materials: A Metallurgical Analysis

“…The diameter of the so obtained pseudo-spherical specimens ([ = 1.9-2.1 mm) was measured and these balls were embedded into the skutterudite matrixes via hot-pressing (56 MPa, 600°C, 2 h in 5 N Ar employing a uniaxial hot press Fig. 1 [36] B (Mo-Ti), [29] C (Ag-Pd), [34] D (Mo-Ti), [31,35] E (Al-Ti), [7,[37][38][39] F (Fe-Ni), [40] G (Al-Ni) [41] W200/250-2200-200-KS). The tablets with a diameter of 10 mm were vacuum-sealed in quartz tubes and heattreated at 600°C for 1100 h. The annealed cylinders were ground to the appearance of the embedded balls, and then polished using standard procedures.…”