SKM 2023 – wissenschaftliches Programm

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 6: Poster

KFM 6.32: Poster

Dienstag, 28. März 2023, 17:00–19:00, P3

Metavalent Bonding empowers the High Thermoelectric Performance in Bi2Te3-based Alloys — •Yinghao Tao — I.Physikalisches Institut of RWTH Aachen

Bi-Te-based alloys show outstanding thermoelectric performance near room temperature due to the large Seebeck coefficient, high electrical conductivity, and low thermal conductivity. Even though the excellent properties of these alloys have been recognised for decades, the origin of these favorable characteristics has not been fully revealed. Very recently, a special combination of properties has been found in group IV-VI and V2-VI3 compounds due to an unconventional bonding mechanism, coined metavalent bonding (MVB). Bi2Te3-based alloys also utilize MVB. This raises the question of whether the excellent thermoelectric performance stems from the MVB. In this work, we have prepared single-crystal BixSb1-xTe3 (x=0.5, 0.6, 0.7) samples by Bridgman oven and then measured the transport properties by thermal transport option (TTO) in PPMS. We have also measured the optical properties and the bond-breaking behavior of these compounds using Fourier-transform infrared spectroscopy (FTIR) and atom probe tomography, respectively. These methods prove the metavalent bonding nature in these compounds. Finally, we relate the favorable transport properties to the close relationship between chemical bonding and the electronic band structure. Metavalent compounds are characterized by a large valley degeneracy, a small band effective mass, and strong phonon anharmonicity. All of these attributes lead to high thermoelectric performance.