材料科学
热电效应
塞贝克系数
兴奋剂
电极
载流子
扩散
化学物理
工作(物理)
密度泛函理论
电荷(物理)
凝聚态物理
光电子学
热力学
物理化学
复合材料
计算化学
量子力学
热导率
物理
化学
作者
Sahar Ayachi,Radhika Deshpande,Prasanna Ponnusamy,Sungjin Park,Jaywan Chung,Su-Dong Park,Byungki Ryu,Eckhard Müller,Johannes de Boor
标识
DOI:10.1016/j.mtphys.2020.100309
摘要
In developing thermoelectric generators, optimizing interfaces between thermoelectric materials and contacting electrodes is a crucial step. Among the tested electrodes for Mg2(Si,Sn)-based generators, Ag shows good adhesion, controllable interfaces and low electrical contact resistances. However, it induces unexpected changes in the Seebeck coefficient of n-type samples, while no change is observed in p-type. In order to understand said behavior, contacting results for Bi-doped Mg2Si, Mg2Sn and Mg2Si1-xSnx with Ag are compared with predictions based on defect formation energies obtained within hybrid-density functional theory (DFT). A qualitative description of the Ag diffusion mechanism in Mg2X is also introduced. Calculation results show that Ag-induced defects have sufficiently low formation energies to influence charge carrier concentrations, particularly Ag substitution on the Mg site (AgMg). AgMg acts as an acceptor and causes a counter-doping effect by compensating the electrons provided by Bi. However, in Li-doped p-type, as Li-defects have the lowest formation energies, a negligible charge carrier concentration change is predicted, which fits with experimental observations. Concerning solid solutions, interpolation from the binaries predicts a similar behavior, which also meets experimental findings. Therefore, this work not only establishes the calculation method and explains the observed effect, but also proves the importance of defects in selecting contacting electrodes.
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