High performance, low cost, and low toxicity have been the main characteristics associated with magnesium-based thermoelectric materials. Nevertheless, the high volatility of magnesium creates challenges in the synthesis of these materials. In this work, n-type Mg₂Ge is synthesized using a solid-state technique, fully characterized, and compared with Mg₂Ge fabricated through different processes. We have found that Bi is an ineffective dopant in Mg₂Ge and precipitates into Mg₂Bi₃. Regardless of the technique used, the loss of Mg by evaporation and formation of precipitates in Bi-doped samples resulted in a low charge carrier concentration and, consequently, a low power factor. The precipitates significantly reduced the lattice thermal conductivity, however, leading to a figure-of-merit, zT, of 0.4 at 725 K, improving the previously reported figure-of-merit, zT, of 0.2 for Sb-doped Mg₂Ge. This work highlights the impact of the fabrication technique on the thermoelectric performance of Mg-based compounds.

中文翻译：

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制备工艺对镁基化合物热电性能的影响-以n型Mg ₂ Ge为例

高性能，低成本和低毒性已成为镁基热电材料的主要特征。然而，镁的高挥发性在这些材料的合成中提出了挑战。在这项工作中，使用固态技术合成了n型Mg ₂ Ge，对其进行了充分表征，并与通过不同工艺制造的Mg ₂ Ge进行了比较。我们发现Bi在Mg ₂ Ge中是无效的掺杂剂，并沉淀到Mg ₂ Bi _3中。不管使用哪种技术，在Bi掺杂样品中蒸发和形成沉淀物都会导致Mg损失，从而导致电荷载流子浓度低，从而导致功率因数较低。沉淀物显着降低了晶格的热导率，但是，导致在725 K下的品质因数zT为0.4，从而改善了先前报道的掺Sb的Mg ₂ Ge的品质因数zT为0.2 。这项工作突出了制造技术对基于Mg的化合物的热电性能的影响。