Theoretical exploration of thermoelectric materials with axis-dependent conduction polarity using first-principles calculations

Axis-dependent conduction polarity exhibits both the p-type and n-type conductions depending on the direction of the temperature gradient. Conventional thermoelectric conversion devices use two types of thermoelectric materials. In 2021, Z_xyT of about 0.7 was achieved with Re₄Si₇[1]. Although axis-dependent conduction polarity has been reported for other materials[2], a material with Z_xyT exceeding 1 has not yet been discovered. In this study, first-principles calculations were performed on existing thermoelectric materials to investigate the axis dependence of the Seebeck coefficient and search for new thermoelectric materials with axis-dependent conduction polarity. We found several materials, such as BaPdS₂, that exhibit axis-dependent conduction polarity with large differences in the Seebeck coefficient between directions. In this presentation, we will discuss the origin of the large difference of the Seebeck coefficient from the band structure point of view.

1) M. R. Scudder et al., Energy Environ. Sci. 14, 4009 (2021).

2) Y. Goto et al., Chem. Mater. 36, 2018 (2024).