Improving electronic properties and mechanical stability of Yb₁₄MnSb₁₁ via W compositing

Many of the missions proposed and successfully completed by the National Aeronautics and Space Administration seek to scientifically investigate remote locations in our solar system, in particular to better understand the origin, evolution and structure of planetary systems. Long-lived, robust power systems are a fundamental capability for such missions, and radioisotope thermoelectric generators (RTGs) have proven to be a reliable power for exploration missions in deep space for the past 50 years. With increasing power needs for future missions, the improvement of thermoelectric materials’ conversion efficiency is necessary. In this paper, we show how compositing with inert metallic inclusions can be efficiently used to improve the electronic properties of Yb₁₄MnSb₁₁. In this study, we found that the power factor of the p-type high temperature material, Yb₁₄MnSb₁₁, increases from ∼8 to ∼11.5 μW cm⁻¹ K⁻² when composited with 5 vol. % W particles. At the same time, the composite samples have a higher thermal conductivity and, therefore, the final zT remains unchanged (∼1.3 at 1273 K). Preliminary hardness tests indicated a qualitative increase in mechanical robustness for the tungsten composite samples. These results can play a relevant role in device design and performance, improving the thermoelectric impedance matching for leg segmentation and helping overcome the intrinsic brittleness of high temperature ceramics such as Yb₁₄MnSb₁₁ for advanced device fabrication.