Electrical and thermal transport properties of YbxCo4Sb12 filled skutterudites with ultrahigh carrier concentrations

For filled skutterudites, element Yb is one of the most common and important fillers. However, the optimal carrier concentration range in YbxCo4Sb12 filled skutterudites has not been determined as a result of the low Yb filling fraction limit. In this study, a non-equilibrium fabrication process (MS-SPS process), consisting of a melt-spinning method and a spark plasma sintering technique, has been applied to prepare YbxCo4Sb12 samples. The Yb filling fraction is successfully extended to 0.35, which provides the possibility to clarify the optimal carrier concentration range for Yb-filled skutterudites. High carrier concentrations, with a maximum of around 1 x 10(21) cm(-3), were achieved in the MS-SPS YbxCo4Sb12 samples due to the significantly enhanced Yb filling fractions. The phase compositions, lattice parameters, electrical and thermal transport properties of the MS-SPS YbxCo4Sb12 samples with high carrier concentrations were systematically investigated. An optimal carrier concentration range of around 5 similar to 6 x 10(20) cm(-3), corresponding to the actual Yb filling fraction of around 0.21 similar to 0.26, has been determined, which displays the highest thermoelectric performance in YbxCo4Sb12 thermoelectric materials. (C) 2015 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.