When band convergence is not beneficial for thermoelectrics.

Band convergence is considered a clear benefit to thermoelectric performance because it increases the charge carrier concentration for a given Fermi level, which typically enhances charge conductivity while preserving the Seebeck coefficient. However, this advantage hinges on the assumption that interband scattering of carriers is weak or insignificant. With first-principles treatment of electron-phonon scattering in the CaMgSb-CaZnSb Zintl system and full Heusler SrSbAu, we demonstrate that the benefit of band convergence can be intrinsically negated by interband scattering depending on the manner in which bands converge.

Machine Learning Chemical Guidelines for Engineering Electronic Structures in Half-Heusler Thermoelectric Materials.

Half-Heusler materials are strong candidates for thermoelectric applications due to their high weighted mobilities and power factors, which is known to be correlated to valley degeneracy in the electronic band structure. However, there are over 50 known semiconducting half-Heusler phases, and it is not clear how the chemical composition affects the electronic structure. While all the n-type electronic structures have their conduction band minimum at either the Γ- or -point, there is more diversity in the p-type electronic structures, and the valence band maximum can be at either the Γ-, -, or -point.

Effect of Two-Dimensional Crystal Orbitals on Fermi Surfaces and Electron Transport in Three-Dimensional Perovskite Oxides.

Perovskite oxides are candidate materials in catalysis, fuel cells, thermoelectrics, and electronics, where electronic transport is vital to their use. While the fundamental transport properties of these materials have been heavily studied, there are still key features that are not well understood, including the temperature-squared behavior of their resistivities. Standard transport models fail to account for this atypical property because Fermi surfaces of many perovskite oxides are low-dimensional and distinct from traditional semiconductors.