Systematic analysis of the interplay between synthesis route, microstructure, and thermoelectric performance in p-type Mg2Si0.2Sn0.8
Systematic analysis of the interplay between synthesis route, microstructure, and thermoelectric performance in p-type Mg2Si0.2Sn0.8
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DOI：
10.1016/j.mtphys.2019.100133
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发表时间：
2019-06
影响因子：
11.5
通讯作者：
H. Kamila;G. Goyal;Aryan Sankhla;P. Ponnusamy;E. Mueller;T. Dasgupta;J. Boor
中科院分区：
文献类型：
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作者：
H. Kamila;G. Goyal;Aryan Sankhla;P. Ponnusamy;E. Mueller;T. Dasgupta;J. Boor
对于热电材料来说，除了成分之外，合成路线是控制热电传输特性以及材料性能的关键因素。在这里，我们系统分析了合成技术对Li掺杂Mg 2 Si 0.2 Sn 0.8 微观结构和热电传输性能的影响。这些样品是使用两种广泛使用但截然不同的合成方法制备的：高能球磨和感应熔炼。微观结构分析（扫描电子显微镜和 X 射线衍射）表明，球磨样品比感应熔炼样品更均匀，其中含有一些富硅 Mg 2 (Si, Sn) 和 MgO 作为第二相。乍一看，两种路线的热电特性性质相似，z T max ≈ 0.4。然而，在单抛物线带模型框架内对高温输运数据的系统分析指出，感应熔化样品的迁移率系统性降低，晶格热导率增加，这可能与微观结构的差异有关。除了在两种合成路线中观察到的声学声子和合金散射之外，迁移率的降低还可以归因于感应熔化样品的进一步载流子散射机制，而晶格导热率的增加是由于晶粒尺寸较大和第二相的存在。因此，这导致球磨样品的热电传输性能显着增强（有效材料参数 β 大 20%），并且预计器件效率的相对差异超过 10%。
For thermoelectric materials, the synthesis route is—besides composition—the crucial factor governing the thermoelectric transport properties and hence the performance of the material. Here, we present a systematic analysis of the influence of the synthesis technique on microstructure and thermoelectric transport properties in Li-doped Mg 2 Si 0.2 Sn 0.8. The samples were prepared using two wide-spread, but quite different synthesis methods: high energy ball milling and induction melting. Microstructural analysis (scanning electron microscopy and X-ray diffraction) reveals that ball milled samples are more homogenous than induction melted ones, which exhibit some Si-rich Mg 2 (Si, Sn) and MgO as secondary phases. On a first glance, the thermoelectric properties are qualitatively similar with z T max≈ 0.4 for both routes. However, a systematic analysis of the high temperature transport data in the framework of a single parabolic band model points out that the induction melted samples have a systematically reduced mobility and increased lattice thermal conductivity which can be tied to the differences in the microstructure. The reduced mobility can be attributed to a further carrier scattering mechanism for the induction melted samples in addition to the acoustic phonon and alloy scattering that are observed for both synthesis routes, while the increased lattice thermal conductivity is because of the larger grain size and presence of secondary phases. In consequence, this leads to significantly enhanced thermoelectric transport properties for ball milled samples (effective material parameter β is∼ 20% larger) and a predicted relative difference in device efficiency of more than 10%.