On the influence of AgMg precursor formation on MgAgSb microstructure and thermoelectric properties

JOURNAL OF ALLOYS AND COMPOUNDS

卷:860

Article

Rodriguez-Barber, Ignacio^1,2  Camut, Julia¹  Luhmann, Laura^1,2  Cowley, Aidan²  Mueller, Eckhard^1,3  de Boor, Johannes¹ 

[1] German Aerosp Ctr, Inst Mat Res, D-51147 Cologne, Germany

[2] European Space Agcy, European Astronaut Ctr, D-51147 Cologne, Germany

[3] Justus Liebig Univ Giessen, Inst Inorgan & Analyt Chem, Heinrich Buff Ring 17, D-35392 Giessen, Germany

关键词: Thermoelectric materials;    Semiconductors;    Mechanical alloying;    Sintering;    Impurities in semiconductors;   

DOI  :  10.1016/j.jallcom.2020.158384

来源: Elsevier

【 摘 要 】

alpha-MgAgSb has been identified as promising thermoelectric material, with peak performance around 300 degrees C, filling the gap between low- and high-temperature thermoelectric materials. The complexity of the Mg-Ag-Sb phase diagram and the sensitivity of the MgAg-Sb synthesis process often leads to impurities appearing in the final samples, which reduce the thermoelectric figure of merit zT. Using a two-step ball milling process, we show that the extent of the AgMg precursor formation has a direct effect on the final composition, mainly with respect to the dyscrasite (Ag3Sb) content. We study how extending the first ball milling step, adding a AgMg sintering step before the second ball milling step or reducing the Ag particle size each affect the overall formation of AgMg. It is shown that lower Ag wt% in said precursor results in lower Ag3Sb content in the final samples, achieving < 1 wt% Ag3Sb when Ag < 1 wt% (in the precursor). This leads to a 23% improvement of zT between 300 and 563 K and a peak value of similar to 1.2 at 500 K. This shows that the complete conversion of Mg and Ag into AgMg is the key for high performance alpha-MgAgSb. (C) 2020 Elsevier B.V. All rights reserved.

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