Interfacial Behavior of Nb-Doped Ti-Al-Based Barrier Layer n-Type Skutterudite Thermoelectric Joints

Abstract Isotope power systems are a key technology for solving the energy bottleneck of deep space exploration, and these thermoelectric (TE) components play an important role in determining the reliability of isotope power systems. TE devices are usually required to provide long-term stable service in high-temperature environments, which can lead to a decrease in the interfacial stability of the device and result in the degradation of the output performance of the isotope power systems. For skutterudite (SKD)-based TE devices, Ti-Al is widely used as the barrier layer joining the SKD and the electrode. To address the problem of increasing contact resistance and decreasing interfacial stability due to the difference in thermal expansion coefficients between TE materials and diffusion-resistant barrier layers in TE devices, in this work we investigated the effect of adding Nb metal on the interfacial stability of n -type TE joints using Ti-Al alloy as the barrier layer. We found that the initial contact resistivity of the Ti-Al-based barrier layer decreased from 5.21 to 3.24 $$\mu \Omega$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>μ</mml:mi> <mml:mi>Ω</mml:mi> </mml:mrow> </mml:math> cm 2 with increasing Nb percentage, demonstrating a decreasing trend. Cu/Ag-Cu/Ti-Al-Nb/n-SKD TE joints with good performance and 10 at.% Nb Ti-Al-Nb as the barrier layer were prepared, and the interfacial resistivity reached 10.23 $$\mu \Omega$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>μ</mml:mi> <mml:mi>Ω</mml:mi> </mml:mrow> </mml:math> cm 2 after aging testing for 384 h. This assessment provided technical support to address the issue of high attenuation rates of high-power isotope power systems.