Camut Julia, Ayachi Sahar, Castillo-Hernández Gustavo, Park Sungjin, Ryu Byungki, Park Sudong, Frank Adina, Stiewe Christian, Müller Eckhard, de Boor Johannes
Institute of Materials Research, German Aerospace Center (DLR), D-51170 Cologne, Germany.
Institute of Inorganic and Analytical Chemistry, Justus Liebig University, D-35392 Giessen, Germany.
Materials (Basel). 2021 Nov 10;14(22):6774. doi: 10.3390/ma14226774.
Thermoelectric generators are a reliable and environmentally friendly source of electrical energy. A crucial step for their development is the maximization of their efficiency. The efficiency of a TEG is inversely related to its electrical contact resistance, which it is therefore essential to minimize. In this paper, we investigate the contacting of an Al electrode on Mg(Si,Sn) thermoelectric material and find that samples can show highly asymmetric electrical contact resistivities on both sides of a leg (e.g., 10 µΩ·cm and 200 µΩ·cm). Differential contacting experiments allow one to identify the oxide layer on the Al foil as well as the dicing of the pellets into legs are identified as the main origins of this behavior. In order to avoid any oxidation of the foil, a thin layer of Zn is sputtered after etching the Al surface; this method proves itself effective in keeping the contact resistivities of both interfaces equally low (<10 µΩ·cm) after dicing. A slight gradient is observed in the n-type leg's Seebeck coefficient after the contacting with the Zn-coated electrode and the role of Zn in this change is confirmed by comparing the experimental results to hybrid-density functional calculations of Zn point defects.
热电发电机是一种可靠且环保的电能来源。其发展的关键一步是实现效率最大化。热电发电机（TEG）的效率与其电接触电阻成反比，因此必须将电接触电阻降至最低。在本文中，我们研究了铝电极与Mg(Si,Sn)热电材料的接触情况，发现样品在一个支腿两侧的电接触电阻率可能呈现高度不对称（例如，一侧为10 μΩ·cm，另一侧为200 μΩ·cm）。差分接触实验表明，铝箔上的氧化层以及将颗粒切割成支腿是导致这种现象的主要原因。为避免铝箔氧化，在蚀刻铝表面后溅射一层薄锌；该方法在切割后能有效保持两个界面的接触电阻率同样低（<10 μΩ·cm）。在与涂锌电极接触后，n型支腿的塞贝克系数出现轻微梯度变化，通过将实验结果与锌点缺陷的杂化密度泛函计算结果进行比较，证实了锌在这种变化中的作用。
