Boosting the thermoelectric performance of Yb-filled skutterudites through the incorporation of YSb nanoprecipitates

To date, the existence state of the Y element in CoSb3-based skutterudites has been perplexing. The previous research has determined that the Y element can be incorporated into skutterudites using a melt-spinning technique followed by hot-press sintering. However, its filling limit is exceedingly low, approximately 0.05. In this study, it is noteworthy that the overall filling quantity exceeds 0.2 in Y0.05YbxCo4Sb12 alloys, and the Y element fails to fill into skutterudites and instead forms a YSb phase. Of particular interest is that the well-formed nanoscale YSb precipitates effectively disrupt phonon transport at phase boundaries, resulting in an extremely low kappa l of similar to 0.5 W m-1 K-1 at 873 K. Moreover, the carrier concentration is finely optimized through the adjustment of Yb. Consequently, a peak ZT of similar to 1.35 at 873 K and an average ZT of 0.95 between 300 K and 873 K are achieved in the x = 0.2 sample. These results can be attributable to the synergistic effects of YSb nanoprecipitates and Yb as effective fillers. This outcome is comparable with most of the reported values and offers new insights into Y-filled-skutterudite-containing thermoelectric materials. In this work, a ZTmax of similar to 1.35 at 873 K is obtained for a Y0.05Yb0.2Co4Sb12 alloy, attributed to the synergistic effects of well-formed nanoscale YSb precipitates and Yb as effective fillers.