High thermoelectric figure of merit ZT of 1.5 and a high average ZT >1.0 between 300 and 850 K can be achieved for Yb-filled CoSb3, which are superior to those of any single-element-filled skutterudite and comparable to the best in this class of materials. The long-term debate about the Yb-filling fraction limit in CoSb3 is clarified to be ~0.29, and the excess Yb mainly forms metallic YbSb2 precipitates. The transport properties of the x >0.35 samples with YbSb2 precipitates are quantitatively reproduced by the Bergman’s composite theory, providing new understanding of the role of Yb in CoSb3.
- Shanyu Wang
- James R Salvador
- Jihui Yang
