Dong Yue, Ding Xueyong, Yan Xinlin, Zhang Long, Tang Zhaohui, Chen Weiliang, Rogl Peter, Paschen Silke
School of Metallurgy, Northeastern University, Shenyang 110819, China.
Institute of Solid State Physics, Vienna University of Technology, Wiedner Hauptstr. 8⁻10, 1040 Vienna, Austria.
Materials (Basel). 2018 Jun 4;11(6):946. doi: 10.3390/ma11060946.
Thermoelectric materials are actively considered for waste heat recovery applications. To improve the heat to electricity conversion efficiency, fundamental understanding on composition, crystal structure, and interrelation with the thermoelectric properties is necessary. Here, we report the chemical and thermoelectric properties of type-I clathrates Ba 8 Ni 3.8 Si x Ge 42.2 - x ( = 0, 10, 20, 42.2), to show that the Si substitution can retain the low lattice thermal conductivity as in pure Ge-based clathrates by adding defects (cage distortion) scattering and/or alloying effect, and the charge carrier concentration can be optimized and thus the electronic properties can be improved by tailoring the vacancy content. We demonstrate the vacancies in the pure Ge-based compound by Rietveld refinement, and possible vacancies in the quaternary compound by transport property measurements. We also show that, for intrinsic property studies in these compounds with such a complex crystal structure, a heat treatment for as cast alloys is necessary for phase purity and composition homogeneity. The highest Z T value of 0.19 at 550 ° C is reached in the compound with x = 10 .
热电材料正被积极考虑用于废热回收应用。为提高热-电转换效率，有必要对成分、晶体结构以及与热电性能的相互关系有基本的了解。在此，我们报告了I型包合物Ba₈Ni₃.₈SixGe₄₂.₂₋ₓ（x = 0、10、20、42.2）的化学和热电性能，以表明Si替代可以通过添加缺陷（笼畸变）散射和/或合金化效应来保持与纯Ge基包合物中类似的低晶格热导率，并且通过调整空位含量可以优化载流子浓度，从而改善电子性能。我们通过Rietveld精修证明了纯Ge基化合物中的空位，并通过输运性质测量证明了四元化合物中可能存在的空位。我们还表明，对于这些具有复杂晶体结构的化合物的本征性质研究，对铸态合金进行热处理对于相纯度和成分均匀性是必要的。x = 10的化合物在550℃时达到最高ZT值0.19。
