Seminar"Resolving Contradiction in Thermoelectric Materials"

Title: "Resolving Contradiction in Thermoelectric Materials"

Speaker: Guangzong Xing, Jilin University, China

Abstract:

High performance thermoelectric (TE) materials require materials with complex electronic structures which may come from complex iso-energy surfaces, multiple valleys, valley anisotropy, heavy-light band combination and band convergence. All these features can not be obtained from the isotropic single parabolic band model because of the inverse relationship of the transport quantities. Here we present a simple transport function that can be directly evaluated based on the first principles electronic structures and the Boltzmann transport theory and it is a universal function that incorporates all these features. We applied the transport function for the screening of 75 potential TE materials and we find an efficient screening with the transport function. The well-known binary TE materials (GeTe, PbTe) can be efficiently screened among all the candidates. Moreover, we also identified two alkali metal Zintl phases (Na₂AuBi, KSnSb), two half-Heuslers (RhNbSn,IrNbSn) and one full-Heusler, Li₂NaSb with favorable electronic properties. In addition, we also did detailed investigation of the thermoelectric properties for cubic GeTe, as well as rhombohedral GeTe, PbTe, SnTe. We found that the high performance observed in p-type cubic GeTe is a consequence of light-heavy band mixture, high valley degeneracy and importantly strong carrier-pocket anisotropy.