Non-stoichiometry related to such an element with high vapor pressure as Mg has been difficult to control, despite its significant influence on the thermoelectric properties of the material. Here, Mg non-stoichiometry and the thermoelectric properties of Mg_2−δSi_1−xSb_x (0 ≤ x ≤ 0.60) are investigated systematically by tuning the Mg partial pressure during annealing. The range of Mg non-stoichiometry Δδ depends on x since the Sb dopant induces Mg vacancies, which are partly filled by Mg atoms in the gas phase according to an equilibrium reaction. The defect association between the Mg vacancies and the Sb dopant decreases Δδ at high Sb contents. The maximum Δδ of 0.016, which corresponds to a carrier concentration range Δn of 4.9 × 10²⁰ cm⁻³, is obtained at x = 0.10. The Seebeck coefficient shows a universal relationship with the carrier concentration, which can be explained by the DFT-calculated band structure within the rigid band approximation. The carrier mobility is reduced significantly as a result of carrier scattering at the Mg-poor grain boundaries. The vacancy formation at the Mg-site, in addition to Si-site substitution for Sb, effectively suppresses the lattice thermal conductivity. The low thermal conductivity on the Mg-poor side increases the maximum zT, while a high energy conversion efficiency is obtained on the Mg-rich side, owing to the high electrical conductivity and resultant large zT at low temperatures. Mg non-stoichiometry is a key factor in tuning the thermoelectric properties of Mg₂Si-based materials and thus its control is essential.

中文翻译：

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非化学计量和Mg的热电性能：Mg的压力受控的退火的效果显著_{2- δ}硅_{1- X} Sb的_X †

尽管这种非化学计量比对材料的热电性能有很大影响，但与这种化学计量有关的非化学计量比仍难以控制，例如镁。在此，Mg的非化学计量比和Mg的热电性质_{2- δ}硅_{1- X} Sb的_X（0≤ X ≤0.60）由调谐系统的研究退火时的Mg的分压。镁的非化学计量Δ的范围δ取决于X由于Sb的掺杂剂诱导的Mg空位，其部分地由Mg原子在气相中根据平衡反应填充。所述Mg空位和Sb的掺杂剂减少Δ之间的缺陷关联δ锑含量高。最大Δ δ的0.016，其对应于一个载流子浓度范围Δ Ñ的4.9×10 ²⁰厘米^-3，在得到X = 0.10。塞贝克系数显示出与载流子浓度的普遍关系，这可以通过在刚性带近似内通过DFT计算的能带结构来解释。由于载流子在贫镁晶界处的散射，载流子迁移率显着降低。除了用Si位代替Sb之外，在Mg位上的空位形成还有效地抑制了晶格热导率。镁贫侧的低热导率增加了最大zT但是，由于高电导率以及在低温下产生的大zT，因此在富Mg侧获得了高能量转换效率。Mg的非化学计量是调节Mg ₂ Si基材料热电性能的关键因素，因此其控制至关重要。