Santos Rafael, Dou Shi Xue, Vashaee Daryoosh, Aminorroaya Yamini Sima
Australian Institute of Innovative Materials (AIIM), Innovation Campus, University of Wollongong, Squire Way, North Wollongong, New South Wales 2500, Australia.
Electrical and Computer Engineering Department, North Carolina State University, Raleigh, North Carolina 27606, United States.
ACS Omega. 2017 Nov 17;2(11):8069-8074. doi: 10.1021/acsomega.7b01389. eCollection 2017 Nov 30.
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 MgGe is synthesized using a solid-state technique, fully characterized, and compared with MgGe fabricated through different processes. We have found that Bi is an ineffective dopant in MgGe and precipitates into MgBi. 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, , of 0.4 at 725 K, improving the previously reported figure-of-merit, , of 0.2 for Sb-doped MgGe. This work highlights the impact of the fabrication technique on the thermoelectric performance of Mg-based compounds.
高性能、低成本和低毒性一直是镁基热电材料的主要特性。然而，镁的高挥发性给这些材料的合成带来了挑战。在这项工作中，采用固态技术合成了n型MgGe，对其进行了全面表征，并与通过不同工艺制备的MgGe进行了比较。我们发现Bi在MgGe中是一种无效的掺杂剂，并沉淀形成MgBi。无论使用何种技术，掺杂Bi的样品中由于镁蒸发导致的镁损失以及沉淀物的形成，都导致了低载流子浓度，进而导致低功率因数。然而，这些沉淀物显著降低了晶格热导率，使得在725 K时优值ZT为0.4，高于之前报道的掺杂Sb的MgGe的优值ZT = 0.2。这项工作突出了制备技术对镁基化合物热电性能的影响。
