Magnesium silicide and its solid solutions are among the most attractive materials for thermoelectric generators in the temperature range of 500–800 K. However, while n‐type Mg₂(Si,Ge,Sn) materials show excellent thermoelectric performance, the corresponding p‐type solid solutions are still inferior, mainly due to less favorable properties of the valence bands compared to the conduction bands. Here, Li doped Mg₂Ge with a thermoelectric figure of merit zT of 0.5 at 700 K is reported, which is four times higher than that of p‐type Mg₂Si and double than that of p‐type Mg₂Sn. The reason for the excellent properties is an unusual temperature dependence of Seebeck coefficient and electrical conductivity compared to a standard highly doped semiconductor. The properties cannot be captured assuming a rigid band structure but well reproduced assuming two parabolic valence bands with a strong temperature dependent interband separation. According to the analysis, the difference in energy between the two bands decrease with temperature, leading to a band convergence at around 650 K and finally to an inversion of the band positions. The finding of a combination of a light and a heavy band that are non‐rigid with temperature can pave the way for further optimization of p‐type Mg₂(Si,Ge,Sn).

中文翻译：

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Mg2Ge中的非刚性带结构可改善热电性能。

硅化镁及其固溶体是温度范围为500–800 K的热电发生器最有吸引力的材料。然而，尽管n型Mg ₂（Si，Ge，Sn）材料显示出出色的热电性能，但相应的p-型固溶体仍然较差，主要是由于价带的导性比导带差。这里，李掺杂Mg的₂的Ge为0.5性能指数ZT，在700 K的热电报道，这比p型的Mg高四倍₂的Si比p型的和双的Mg ₂锡 之所以具有优异的性能，是因为与标准的高掺杂半导体相比，塞贝克系数和电导率具有不寻常的温度依赖性。假定刚性带结构不能捕获这些特性，但是假定两个抛物价带具有强的温度依赖性带间分隔，则可以很好地再现这些特性。根据分析，两个频带之间的能量差随温度降低而减小，导致频带在650 K附近收敛，最后导致频带位置反转。发现不随温度变化的轻带和重带的组合可以为进一步优化p型Mg ₂（Si，Ge，Sn）铺平道路。