Journal article

Publication year: 2020

Journal: Advanced Science

Volume number: 7

Issue number: 12

eISSN: 2198-3844

Open access status: Green

DOI Link: https://doi.org/10.1002/advs.202000070

Publisher: Wiley

Abstract: 
Magnesium silicide and its solid solutions are among the most attractive materials for thermoelectric generators in the temperature range of 500-800 K. However, while n-type Mg-2(Si,Ge,Sn) materials show excellent thermoelectric performance, the corresponding p-type solid solutions are still inferior, mainly due to less favorable properties of the valence bands compared to the conduction bands. Here, Li doped Mg2Ge with a thermoelectric figure of merit zT of 0.5 at 700 K is reported, which is four times higher than that of p-type Mg2Si and double than that of p-type Mg2Sn. The reason for the excellent properties is an unusual temperature dependence of Seebeck coefficient and electrical conductivity compared to a standard highly doped semiconductor. The properties cannot be captured assuming a rigid band structure but well reproduced assuming two parabolic valence bands with a strong temperature dependent interband separation. According to the analysis, the difference in energy between the two bands decrease with temperature, leading to a band convergence at around 650 K and finally to an inversion of the band positions. The finding of a combination of a light and a heavy band that are non-rigid with temperature can pave the way for further optimization of p-type Mg-2(Si,Ge,Sn).

Harvard Citation style: Kamila, H., Sankhla, A., Yasseri, M., Mueller, E. and de Boor, J. (2020) Non-Rigid Band Structure in Mg₂Ge for Improved Thermoelectric Performance, Advanced Science, 7(12), Article 2000070. https://doi.org/10.1002/advs.202000070

APA Citation style: Kamila, H., Sankhla, A., Yasseri, M., Mueller, E., & de Boor, J. (2020). Non-Rigid Band Structure in Mg₂Ge for Improved Thermoelectric Performance. Advanced Science. 7(12), Article 2000070. https://doi.org/10.1002/advs.202000070