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 (NASA) seek to investigate remote locations in our solar system to better understand the formation of our planet and the evolution of the solar system. Reliable, long-lived and robust power systems are a fundamental requisite for spacecraft, and radioisotope thermoelectric generators (RTGs) have been a proven source of electrical power for exploration missions in deep space for more than 40 years. With increasingly ambitious missions planned for the future, an improvement in the conversion efficiency of the thermoelectric materials in an RTG would offer great benefits. 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 μWcm-1K-2 when composited with 5vol% W . At the same time, the composite samples have a higher thermal conductivity and therefore the final zT remains unchanged (~1.3 at 1273K). Furthermore, preliminary hardness tests showed a qualitative increase in mechanical robustness for the tungsten composite samples. These results can have a relevant role in device design and performance, improving the impedance matching for leg segmentation and helping overcoming the intrinsic brittleness of high temperature ceramics like Yb14MnSb11 for advanced device fabrication.