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JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
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AMER CHEMICAL SOC
DOI: 10.1021/jacs.2c12877
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GeMnTe2 adopts a cubic rock salt structure and can be tuned by alloying with SbTe to achieve high power factor and low thermal conductivity. The GeMnTe2-15.1%SbTe composition exhibits a ZTave of 0.96 in the temperature range of 400-823 K.
GeMnTe2 adopts a cubic rock salt structure and is a promising mid-temperature thermoelectric material. The pair distribution function analysis of neutron total scattering data, however, indicates that GeMnTe2 is locally distorted from the ideal rock salt structure with Ge2+ cations being discordant and displaced similar to 0.3 A off the octahedron center. By alloying GeMnTe2 with SbTe, the carrier concentration can be tuned in GeMnTe2-x%SbTe (x = 15.1), leading to converged multiple broad valence bands and a high Seebeck coefficient of >200 mu V K-1 from 300 to 823 K. The system exhibits a large density-of-state effective mass of >10 me and a high weighted mobility of 80 cm2 V-1 s-1, leading to a power factor of 15 mu Wcm-1 K-2 at 823 K. The composition GeMnTe2-15.1%SbTe exhibits very low lattice thermal conductivity of similar to 0.5 Wm-1 K-1 at 823 K, attributed to the combination of off-centering cations in the rock salt structure, Ge/Mn positional disorder, dislocations, and abundant Ge-rich and Mn-rich nanoparticles. A ZT value of similar to 1.5 can be achieved for GeMnTe2-15.1%SbTe with a ZTave of 0.96 in the temperature range of 400-823 K.
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