Solid-Liquid Interdiffusion (SLID) Bonding of p-Type Skutterudite Thermoelectric Material Using Al-Ni Interlayers

Abstract

Over the past few years, significant progress towards implementation of environmentally sustainable and cost-effective thermoelectric power generation has been made. However, the reliability and high-temperature stability challenges of incorporating thermoelectric materials into modules still represent a key bottleneck. Here, we demonstrate an implementation of the Solid-Liquid Interdiffusion technique used for bonding Mmy(Fe,Co)4Sb12 p-type thermoelectric material to metallic interconnect using a novel aluminium–nickel multi-layered system. It was found that the diffusion reaction-controlled process leads to the formation of two distinct intermetallic compounds (IMCs), Al3Ni and Al3Ni2, with a theoretical melting point higher than the initial bonding temperature. Different manufacturing parameters have also been investigated and their influence on electrical, mechanical and microstructural features of bonded components are reported here. The resulting electrical contact resistances and apparent shear strengths for components with residual aluminium were measured to be (2.8 ± 0.4) × 10−5 Ω∙cm2 and 5.1 ± 0.5 MPa and with aluminium completely transformed into Al3Ni and Al3Ni2 IMCs were (4.8 ± 0.3) × 10−5 Ω∙cm2 and 4.5 ± 0.5 MPa respectively. The behaviour and microstructural changes in the joining material have been evaluated through isothermal annealing at hot-leg working temperature to investigate the stability and evolution of the contact.

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

“…CoSb 3 -based filled skutterudites are considered as one kind of the most promising mid-temperature TE materials not only due to their good TE performance but also due to their low cost, high mechanical strength, and high thermal stability. ,− Hence, CoSb 3 -based filled skutterudites are popular for fabricating TE devices. ,, However, CoSb 3 -based TE materials can also have great interdiffusion or chemical reaction with most of the metal and alloy electrodes in the high-temperature range. ,, 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, ,− Ni, Co, Mo, Nb, Ti–Al alloys, , Al–Ni alloys, TaN–Ta–TaN alloys, Fe–Ni alloys, Ti–Mo alloys, and Co–Mo alloys . 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. ,,,, Gu et al used the Ti–Al alloy as a barrier layer for n-type Yb 0.6 Co 4 Sb 12 TE materials, revealing that the intermetallic compounds of Ti 3 Al and TiAl formed in Ti–Al alloys can effectively hinder further interfacial diffusion.…”

“…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.…”

“…(a) Aging-time-dependent shear strength of Ti−Al−Si/CoSb 3 joints and Ti−Ni/CoSb 3 joints for the aging test at 500 °C. (b)Comparison of the shear strength of our TE joints after 16-day aging at 500 °C with other reported CoSb 3 -based TE joints after aging using different diffusion barrier materials 17,33,34.…”

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.…”

Intermetallic Growth at the Interfaces Between Zn4Sb3 Thermoelectric Material and Various Metallic Electrodes

“…[10] Moreover, brazing further entails the risks of thermal cracking and interfacial diffusion because the high operating temperature of the brazing process is usually the melting temperature of these TE materials. [13,14] Thus, various methods have been developed to solve this problem in the manufacturing of medium-or high-temperature thermoelectric modules. Weinstein et al adopted spark plasma sintering (SPS) to join a medium temperature PbTe element with an Fe electrode.…”