Page 264 - Read Online

Duparchy et al. Energy Mater. 2025, 5, 500134 Energy Materials
DOI: 10.20517/energymater.2025.51

Article Open Access

Poorer is better: towards robust, high performance

Mg (Si,Sn) thermoelectric material by avoiding
2
excess Mg

1,*
2
2
1
1
Amandine Duparchy , Harshita Naithani , Sanyukta Ghosh , Michael Parzer , Fabian Garmroudi , Eckhard
1,3
Müller , Johannes de Boor 1,4,*
1
Institute for Frontier Materials on Earth and in Space, German Aerospace Center (DLR), Cologne 51147, Germany.
2
Institute of Solid-State Physics, TU Wien, Vienna 1040, Austria
3
Institute of Inorganic and Analytical Chemistry, Justus Liebig University Giessen, Giessen 35392, Germany.
4
Institute of Technology for Nanostructures (NST) and CENIDE, University of Duisburg-Essen, Faculty of Engineering, Duisburg
47057, Germany.
* Correspondence to: Amandine Duparchy and Prof. Johannes de Boor, Institute of Materials Research, German Aerospace
Center (DLR), Linder Höhe, Cologne 51147, Germany. E-mail: amandine.duparchy@dlr.de; Johannes.deBoor@dlr.de
How to cite this article: Duparchy, A.; Naithani, H.; Ghosh, S.; Parzer, M.; Garmroudi, F.; Müller, E.; de Boor, J. Poorer is better:
towards robust, high performance Mg (Si,Sn) thermoelectric material by avoiding excess Mg. Energy Mater. 2025, 5, 500134.
2
https://dx.doi.org/10.20517/energymater.2025.51
Received: 28 Feb 2025 First Decision: 30 Apr 2025 Revised: 7 May 2025 Accepted: 16 May 2025 Published: 9 Jul 2025
Academic Editor: Yizhong Huang Copy Editor: Ping Zhang Production Editor: Ping Zhang

Abstract
Mg (Si,Sn)-based semiconductors constitute promising thermoelectrics (TE), in particular as n-type materials.
2
These are usually synthesized under Mg-excess to compensate for losses of Mg during synthesis and achieve the
high carrier concentration required for optimal performance. However, this usage of excess Mg leads to loosely
bound Mg in the material which is easily lost during operation, leading to a fast and massive degradation of the TE
performance. In this work, we introduce Mg-poor n-type Mg (Si,Sn), avoiding excess and loosely bound Mg. We
2
find that (i) employing relatively large nominal Mg deficiency leads nevertheless to single-phase, Mg-poor
Mg (Si,Sn) by a self-adjustment of the composition during sintering, and (ii) that despite showing a lower dopant
2
efficiency, Sb can be employed to achieve the required optimum carrier concentration, resulting in a figure of merit
of zT = 1.2 ± 0.2 at 700 K, comparable to Mg-rich samples. This is confirmed by a comparison of Mg-rich and
Mg-poor samples in a single parabolic band model which reveals similar microscopic material parameters such as
weighted mobility and scattering constants. Finally, we compare Mg-poor synthesized samples with initially
Mg-rich ones that experienced Mg loss. Despite similar global compositions we identify grain boundary scattering
to be more pronounced in Mg-depleted samples, marking one of the fundamental reasons for the performance
degradation of synthesized Mg-rich synthesized samples. Overall, this work highlights the importance of grain

© The Author(s) 2025. Open Access This article is licensed under a Creative Commons Attribution 4.0
International License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, sharing,
adaptation, distribution and reproduction in any medium or format, for any purpose, even commercially, as
long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and
indicate if changes were made.

www.oaepublish.com/energymater