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

Abstract

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 Y_0.05Yb_xCo₄Sb₁₂ 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 κ_l of ∼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 ∼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.