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

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 Mm_y(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.