Abstract

In this work, silicon and higher manganese silicide (HMS) bulk nanocomposites were synthesized, Si_100-x(HMS)_x, where x is 10–50, and their thermoelectric properties were studied. The powders of Si and Mn in a stoichiometric ratio were mixed by a ball milling, followed by hot-pressing to obtain the Si + HMS bulk nanocomposite samples. Every bulk sample was highly dense, with a density of over 90% of its theoretical value. The x-ray diffraction analysis revealed that only the Si and HMS phases, without any impurity phase, were obtained. The fractured surface morphology showed that the composites consisted of micro-sized Si matrix grains with the HMS nanodots homogenously distributed within the grains. The thermoelectric studies showed that thermal conductivity decreased with a higher concentration of HMS, mainly due to the reduction of lattice thermal conductivity. It was believed to be the presence of the HMS nanodots which effectively scattered phonon transport. Furthermore, the addition of HMS increased charge carrier concentration. Hence, the Seebeck coefficient decreased, and the electrical conductivity increased with increasing HMS content. However, the presence of the HMS nanodots also contributed to strong scattering of charge carriers. The charge mobility was reduced significantly for the composite samples compared to the bulk Si sample. Therefore, the electrical conductivity is relatively low compared to the reported values in the literature. The dimensionless figure-of-merit (ZT) was improved in the nanocomposite samples compared to the bulk Si sample, and the values were largest for the sample with x = 50.

中文翻译：

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硅和高锰硅化物块状纳米复合材料的合成及其热电性能

摘要

在这项工作中，合成了硅和高锰硅化物（HMS）块状纳米复合材料Si _{100- x}（HMS）_x，其中x为10-50，并对其热电性能进行了研究。通过球磨混合以化学计量比混合的Si和Mn粉末，然后热压以获得Si + HMS块状纳米复合材料样品。每个散装样品都是高密度的，密度超过其理论值的90％。X射线衍射分析表明，仅获得了Si和HMS相，没有任何杂质相。断裂的表面形态表明，复合材料由细小的Si基晶粒组成，HMS纳米点均匀分布在晶粒内。热电研究表明，随着HMS浓度的增加，热导率降低，这主要归因于晶格热导率的降低。据信存在有效分散声子传输的HMS纳米点。此外，添加HMS可增加电荷载流子浓度。因此，塞贝克系数降低，而电导率随HMS含量的增加而增加。但是，HMS纳米点的存在也有助于电荷载流子的强烈散射。与体硅样品相比，复合材料样品的电荷迁移率显着降低。因此，与文献中报道的值相比，电导率相对较低。与块状硅样品相比，纳米复合材料样品的无量纲品质因数（ZT）有所改善，并且值最大。HMS纳米点的存在也有助于电荷载流子的强烈散射。与体硅样品相比，复合材料样品的电荷迁移率显着降低。因此，与文献中报道的值相比，电导率相对较低。与块状硅样品相比，纳米复合材料样品的无量纲品质因数（ZT）有所改善，并且值最大。HMS纳米点的存在也有助于电荷载流子的强烈散射。与体硅样品相比，复合材料样品的电荷迁移率显着降低。因此，与文献中报道的值相比，电导率相对较低。与块状硅样品相比，纳米复合材料样品的无量纲品质因数（ZT）有所改善，并且值最大。x = 50。