Achieving Reliable CoSb3 based thermoelectric joints with low contact resistivity using a high-entropy alloy diffusion barrier layer

Abstract

Skutterudite (SKD) thermoelectric materials have high conversion efficiency, great mechanical properties, and economical practicability in the medium temperature range (500–550 °C). They need to be joined with metal electrodes to form a thermoelectric power generation device during application. However, high contact resistivity, severe element diffusion, and large coefficient of thermal expansion mismatch are main obstacles for their applications. To address these issues, a FeCoNiCrMo high-entropy alloy diffusion barrier layer was designed and prepared using an arc smelting method in this paper. Effect of heating temperatures on the microstructure and properties of the bonded joints were investigated. The maximum shear strength was 21.6 Mpa and the corresponding reaction layer thickness, contact resistivity were 3.77 μm, 1.8 μΩcm2 respectively at 600 °C, 40 MPa, 10 min. Shear strength dropped down to 18.8 MPa and the contact resistivity increased to 4.2 μΩ cm2 after aging for 640 h. Numerical model was established and it predicted that the contact resistivity would keep lower than 6.5 μΩ cm2 (300 h, 100 days) and 11 μΩ cm2 (8760 h, 1 year) and the reaction layer thickness would not exceed 25 μm (2400 h, 100 days) and 45 μm (8760 h, 1 year).