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Recently, Jiang Peng, Research Fellow of the State Key Laboratory of Catalysis of the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, and Bao Xunhe (Team 502), Academician of the Chinese Academy of Sciences, have made new progress in thermoelectric materials research. The strategy of using high-entropy alloys to increase the symmetry of crystal structures has been successful. The GeSe crystal structure is controlled, and the thermoelectric properties of the GeSe material are greatly improved. The relevant research results are published in "Angew. Chem. Int. Ed., DOI: 10.1002/anie.201708134".
Thermoelectric technology can realize the mutual transformation between thermal energy and electrical energy. As a clean energy conversion method, it has broad application prospects. However, traditional high-performance thermoelectric materials usually contain Bi, Pb, Te and other expensive and highly toxic elements, hindering their large-scale application. GeSe is a potentially environmentally friendly thermoelectric material, which is theoretically predicted to have excellent thermoelectric properties. For a long time, due to the lack of effective doping methods, its carrier concentration and conductivity are very low, which seriously affects its thermoelectricity. The performance has been improved. Up to now, the reported zT experimental value of GeSe materials is up to 0.2.
In this work, the team adopted a high entropy alloy to increase the symmetry of the structure. By alloying GeSe with AgSbSe2, the controllable transformation of the GeSe crystal structure from an orthorhombic to a rhombohedral was successfully achieved. . Studies have shown that this higher symmetry trigonal crystal structure has high carrier concentration (~1020 cm-3), multiple energy bands, and high effective mass, and thermoelectric properties are significantly improved. The zT of GeAg0.2Sb0.2Se1.4 can reach 0.86 at 710K, which is 18 times higher than the zT value of the pure GeSe with an orthorhombic structure, and is 4 times higher than the zT value reported in the literature.
The research work not only shows that GeSe-based thermoelectric materials have good potential for development, but also a new method developed to improve the thermoelectric properties through high entropy alloys to regulate the crystal structure is expected to be applied to other thermoelectric material systems.
The theoretical part of this work was supported by G. Jeffrey Snyder, a professor at Northwestern University in the United States, and Zhuang Yan, a researcher at Fujian Institute of Materials Structure, Chinese Academy of Sciences. Electron microscopy characterization work was done by Ge Binghui, associate researcher at the Institute of Physics, Chinese Academy of Sciences. The research work was funded by the National Natural Science Foundation of China and Dalian Institute of Natural Resources.
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