Institute for Computational Materials Science, School of Physics and Electronics, Henan University, Kaifeng, 475004, China.
Guizhou Provincial Key Laboratory of Computational Nano-Material Science, Guizhou Education University, 115 Gaoxin Road, Guiyang, 550018, China.
Sci Rep. 2017 May 31;7(1):2572. doi: 10.1038/s41598-017-02808-8.
Engineering atomic-scale native point defects has become an attractive strategy to improve the performance of thermoelectric materials. Here, we theoretically predict that Ag-Mg antisite defects as shallow acceptors can be more stable than other intrinsic defects under Mg-poor‒Ag/Sb-rich conditions. Under more Mg-rich conditions, Ag vacancy dominates the intrinsic defects. The p-type conduction behavior of experimentally synthesized α-MgAgSb mainly comes from Ag vacancies and Ag antisites (Ag on Mg sites), which act as shallow acceptors. Ag-Mg antisite defects significantly increase the thermoelectric performance of α-MgAgSb by increasing the number of band valleys near the Fermi level. For Li-doped α-MgAgSb, under more Mg-rich conditions, Li will substitute on Ag sites rather than on Mg sites and may achieve high thermoelectric performance. A secondary valence band is revealed in α-MgAgSb with 14 conducting carrier pockets.
工程原子尺度本征点缺陷已成为提高热电材料性能的一种有吸引力的策略。在这里，我们从理论上预测，Ag-Mg 反位缺陷作为浅受主在 Mg 贫-Ag/Sb 富条件下比其他本征缺陷更稳定。在更富 Mg 的条件下，Ag 空位主导本征缺陷。实验合成的 α-MgAgSb 的 p 型传导行为主要来自 Ag 空位和 Ag 反位（Mg 位上的 Ag），它们作为浅受主。Ag-Mg 反位缺陷通过增加费米能级附近能带谷的数量显著提高了 α-MgAgSb 的热电性能。对于 Li 掺杂的 α-MgAgSb，在更富 Mg 的条件下，Li 将取代 Ag 位而不是 Mg 位，并且可能获得高的热电性能。α-MgAgSb 中揭示了一个二次价带，有 14 个传导载流子口袋。
