The filling fraction limitation (FFL) in n-type CoSb 3 skutterudites is far below that of p-type (Fe,Co)Sb 3 -based skutterudites, and it is critical to increase FFL for accomplishing high thermoelectric figure of merit (ZT max ). Here, a series of Yb x Co 4-y Fe y Sb 12 alloys with x = 0.25-0.5 and y = 0.1-0.5 were synthesized, which demonstrate a clear increase of the FFL of Yb from ∼0.3 in CoSb 3 to 0.5. Ultralow thermal conductivities of 2.0-2.5 W/m·K at 300 K and 1.75 W/m·K at ∼600 K have been achieved, which are the lowest values reported among skutterudite materials and comparable with p-type skutterudites. These ultralow thermal conductivities result from the combination of secondary phase scattering and phonon scattering from dynamic electron exchange between Fe 2+ and Co 3+ . High ZT max values of 1.28 at 740 K and 1.34 at 780 K are obtained, which are among the best values reported in the temperature range of 740-800 K. The temperature at which maximum ZT max appears is shifted below 850 K. These results are highly exciting toward the development of multistage segmented and cascade thermoelectric power generators for in-air operations.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)
- Materials Chemistry