Abstract

It is crucial to reach a sufficiently high carrier concentration in order to optimize the thermoelectric (TE) material in the development of Mg2X (X= Si, Ge, and Sn)-based TE generators. While n-type Mg2(Si,Sn) has excellent TE properties, p-type shows suboptimal TE performance because of insufficient carrier concentration, in particular for Mg2Si and Si-rich Mg2(Si,Sn). A systematic investigation of Li-doped Mg2Si1-xSnx has been performed as Li, in contrast to other typical dopants, has a high solubility in the material system and has been shown to yield the highest reported carrier concentrations. We observe that the carrier concentration increases with Li content, but the dopant efficiency decreases. With respect to the Si:Sn ratio, we find a clear increase in maximum achievable carrier concentration and dopant efficiency with increasing Sn content. The trends can be understood by employing defect formation energies obtained within the hybrid-density functional theory (DFT) for the binaries. Further, we use a linear interpolation of the hybrid-DFT results from the binaries to the ternary Mg2(Si,Sn) compositions and a simple single parabolic band model to predict the maximal achievable carrier concentration for the solid solutions, providing a simple guideline for experimental work. Finally, we show that the approach is transferable to other material classes. This work highlights that, besides dopant solubility, the interplay between intrinsic and extrinsic defects determines the achievable carrier concentration.

Details

Title
Understanding the dopability of p-type Mg2(Si,Sn) by relating hybrid-density functional calculation results to experimental data
Author
Hasbuna Kamila 1   VIAFID ORCID Logo  ; Ryu, Byungki 2   VIAFID ORCID Logo  ; Ayachi, Sahar 1 ; Sankhla, Aryan 1   VIAFID ORCID Logo  ; Mueller, Eckhard 3 ; de Boor, Johannes 4   VIAFID ORCID Logo 

 German Aerospace Center (DLR), Institute of Materials Research , D–51147 Koeln, Germany 
 Energy Conversion Research Center, Electrical Materials Research Division, Korea Electrotechnology Research Institute (KERI) , Changwon 51543, Republic of Korea 
 German Aerospace Center (DLR), Institute of Materials Research , D–51147 Koeln, Germany; Justus Liebig University Giessen, Institute of Inorganic and Analytical Chemistry , D–35392 Giessen, Germany 
 German Aerospace Center (DLR), Institute of Materials Research , D–51147 Koeln, Germany; University of Duisburg–Essen, Institute of Technology for Nanostructures (NST) , D–47057 Duisburg, Germany 
First page
035001
Publication year
2022
Publication date
Jul 2022
Publisher
IOP Publishing
e-ISSN
25157655
Source type
Scholarly Journal
Language of publication
English
ProQuest document ID
2672375533
Copyright
© 2022 The Author(s). Published by IOP Publishing Ltd. This work is published under http://creativecommons.org/licenses/by/4.0 (the “License”). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.