Li Xu-Guang, Liu Wei-Di, Li Shuang-Ming, Li Dou, Zhu Jia-Xi, Feng Zhen-Yu, Yang Bin, Zhong Hong, Shi Xiao-Lei, Chen Zhi-Gang
State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, China.
Australian Institute of Bioengineering and Nanotechnology, The University of Queensland, Brisbane, QLD 4072, Australia.
Materials (Basel). 2021 Nov 11;14(22):6810. doi: 10.3390/ma14226810.
CoSb-based skutterudite is a promising mid-temperature thermoelectric material. However, the high lattice thermal conductivity limits its further application. Filling is one of the most effective methods to reduce the lattice thermal conductivity. In this study, we investigate the Ce filling limit and its influence on thermoelectric properties of p-type FeCoSb-based skutterudites grown by a temperature gradient zone melting (TGZM) method. Crystal structure and composition characterization suggests that a maximum filling fraction of Ce reaches 0.73 in a composition of CeFeCoSb prepared by the TGZM method. The Ce filling reduces the carrier concentration to 1.03 × 10 cm in the CeFeCoSb, leading to an increased Seebeck coefficient. Density functional theory (DFT) calculation indicates that the Ce-filling introduces an impurity level near the Fermi level. Moreover, the rattling effect of the Ce fillers strengthens the short-wavelength phonon scattering and reduces the lattice thermal conductivity to 0.91 W m K. These effects induce a maximum Seebeck coefficient of 168 μV K and a lowest of 1.52 W m K at 693 K in the CeFeCoSb, leading to a peak value of 0.65, which is 9 times higher than that of the unfilled FeCoSb.
基于CoSb的方钴矿是一种很有前景的中温热电材料。然而，高晶格热导率限制了其进一步应用。填充是降低晶格热导率最有效的方法之一。在本研究中，我们研究了Ce填充极限及其对通过温度梯度区熔（TGZM）法生长的p型FeCoSb基方钴矿热电性能的影响。晶体结构和成分表征表明，通过TGZM法制备的CeFeCoSb成分中Ce的最大填充分数达到0.73。Ce填充使CeFeCoSb中的载流子浓度降低至1.03×10 cm，导致塞贝克系数增加。密度泛函理论（DFT）计算表明，Ce填充在费米能级附近引入了一个杂质能级。此外，Ce填充原子的晃动效应增强了短波长声子散射，并将晶格热导率降低至0.91 W m K。这些效应在CeFeCoSb中于693 K时产生了168 μV K的最大塞贝克系数和1.52 W m K的最低热导率，导致峰值ZT为0.65，比未填充的FeCoSb高9倍。
