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首页> 外文期刊>RSC Advances >Electronic structure and thermoelectric properties of the Zintl compounds Sr5Al2Sb6 and Ca5Al2Sb6: first-principles study
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Electronic structure and thermoelectric properties of the Zintl compounds Sr5Al2Sb6 and Ca5Al2Sb6: first-principles study

机译：Zintl化合物Sr5Al2Sb6和Ca5Al2Sb6的电子结构和热电性质：第一性原理研究

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Previous experimental work showed that Zn-doping only slightly increased the carrier concentration of Sr5Al2Sb6 and the electrical conductivity improved barely, which is very different from the results of Zn-doping in Ca5Al2Sb6. To understand their different thermoelectric behaviors, we investigated their stability, electronic structure, and thermoelectric properties using first-principles calculations and the semiclassical Boltzmann theory. We found that the low carrier concentration of Zn-doped Sr5Al2Sb6 mainly comes from its high positive formation energy. Moreover, we predict that a high hole concentration can possibly be realized in Sr5Al2Sb6 by Na or Mn doping, due to the negative and low formation energies of Na- and Mn-doped Sr5Al2Sb6, especially for Mn doping (-6.58 eV). For p-type Sr5Al2Sb6, the large effective mass along Gamma-Y induces a large Seebeck coefficient along the y direction, which leads to the good thermoelectric properties along the y direction. For p-type Ca5Al2Sb6, the effective mass along Gamma-Z is always smaller than those along the other two directions with increasing doping degree, which induces its good thermoelectric properties along the z direction. The analysis of the weight mobility of the two compounds confirms this idea. The calculated band structure shows that Sr5Al2Sb6 has a larger band gap than Ca5Al2Sb6. The relatively small band gap of Ca5Al2Sb6 mainly results from the appearance of a high density-of-states peak around the conduction band bottom, which originates from the Sb-Sb antibonding states in it.
机译：先前的实验工作表明，Zn掺杂仅略微增加了Sr5Al2Sb6的载流子浓度，而电导率几乎没有提高，这与Ca5Al2Sb6中Zn掺杂的结果有很大不同。为了了解它们的不同热电行为，我们使用第一性原理计算和半经典玻尔兹曼理论研究了它们的稳定性，电子结构和热电特性。我们发现，掺杂锌的Sr5Al2Sb6的低载流子浓度主要来自其高正形成能。此外，我们预测，由于Na和Mn掺杂的Sr5Al2Sb6的负和低形成能，特别是对于Mn掺杂（-6.58 eV），通过Na或Mn掺杂可以在Sr5Al2Sb6中实现高空穴浓度。对于p型Sr5Al2Sb6，沿Gamma-Y的大有效质量沿y方向会引起较大的塞贝克系数，这会导致沿y方向具有良好的热电特性。对于p型Ca5Al2Sb6，随着掺杂程度的提高，沿Gamma-Z的有效质量始终小于沿其他两个方向的有效质量，这导致其沿z方向的良好热电性能。对两种化合物的重量迁移率的分析证实了这一想法。计算出的能带结构表明，Sr5Al2Sb6的带隙比Ca5Al2Sb6大。 Ca5Al2Sb6的带隙相对较小，主要是由于在导带底部周围出现了高态密度峰，这是由其中的Sb-Sb反键态引起的。

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