First-principles study of the axis-dependent conduction polarity of Mg₃Bi₂

Mg₃Sb₂ exhibits remarkable thermoelectric properties with a ZT value exceeding 1. In contrast, Mg₃Bi₂ shows lower thermoelectric performance due to its semimetallic state. However, axis-dependent conduction polarity, where the sign of the Seebeck coefficient varies with crystallographic orientation, has been observed in Mg₃Bi₂[1]. This characteristic feature of this material suggests potential applications as a transverse thermoelectric device. The axis-dependent conduction polarity of Mg₃Bi₂ originates from the band dispersion around the Fermi level. The band structure of Mg₃Bi₂ includes both Dirac cone-like valence and conduction bands at the Γ point and multi-valley bands near the L^* point, which are expected to have different relaxation times. In this study, we evaluate the electron relaxation time in Mg₃Bi₂ and calculate its thermoelectric properties. The presentation will discuss the detailed band structure of Mg₃Bi₂ and the relaxation time.

[1] Y. Goto et al., Chem. Mater. 36, 2018 (2024)