The filling fraction limitation (FFL) in n-type CoSb₃ skutterudites is far below that of p-type (Fe,Co)Sb₃-based skutterudites, and it is critical to increase FFL for accomplishing high thermoelectric figure of merit (ZT_max). Here, a series of Yb_xCo_4–yFe_ySb₁₂ 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 CoSb₃ 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 Fe²⁺ and Co³⁺. 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.

中文翻译：

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超低导热率增强了Yb单填充方钴矿的热电性能

n型CoSb _3型方钴矿的填充分数限制（FFL）远低于p型（Fe，Co）Sb ₃型方钴矿的填充分数限制，为实现高热电品质因数（ZT _max）。在此，一连串的Yb _X钴_{4 -y}铁_ý锑_12种合金X = 0.25-0.5和ÿ = 0.1-0.5合成，其在表现出的CoSb从~0.3 Yb中FFL的明显增加₃到0.5。在300 K时达到2.0-2.5 W / m·K的超低导热率，在600 K时达到1.75 W / m·K的超低导热率，这是方钴矿材料中报道的最低值，可与p型方钴矿媲美。这些超低热导率是由于Fe ²⁺和Co ³⁺之间动态电子交换引起的次级相散射和声子散射的结合而产生的。高ZT_最大值在740 K和1.28的值1.34在780 K的获得，这是最好的值中报道的温度范围内的740-800 K.的温度在最大ZT_最大 出现在850 K以下。这些结果对于开发用于空中操作的多级分段和级联热电发电机非常令人兴奋。