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Non‐Rigid Band Structure in Mg2Ge for Improved Thermoelectric Performance

Kamila, Hasbuna and Sankhla, Aryan and Yasseri, Mohammad and Müller, Eckhard and de Boor, Johannes (2020) Non‐Rigid Band Structure in Mg2Ge for Improved Thermoelectric Performance. Advanced Science, 7 (200007). Wiley. doi: 10.1002/advs.202000070. ISSN 2198-3844.

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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 Mg2(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 Mg2(Si,Ge,Sn).

Item URL in elib:https://elib.dlr.de/137152/
Document Type:Article
Title:Non‐Rigid Band Structure in Mg2Ge for Improved Thermoelectric Performance
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Kamila, Hasbunagerman aerospace center, institute of materials research, köln, germanyUNSPECIFIED
Sankhla, Aryangerman aerospace center, institute of materials research, köln, germanyhttps://orcid.org/0000-0002-1527-6902
Yasseri, Mohammadgerman aerospace center, institute of materials research, köln, germany and justus liebig university giessen, institute of inorganic and analytical chemistry, 35392 giessen, germanyUNSPECIFIED
Müller, EckhardGerman Aerospace Center, Institute of Materials Research, Köln, Germany and Justus Liebig University Giessen, Institute of Inorganic and Analytical Chemistry, 35392 Giessen, GermanyUNSPECIFIED
de Boor, JohannesGerman aerospace center, institute of materials research, köln, germanyhttps://orcid.org/0000-0002-1868-3167
Date:30 April 2020
Journal or Publication Title:Advanced Science
Refereed publication:Yes
Open Access:Yes
Gold Open Access:Yes
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:7
DOI :10.1002/advs.202000070
Publisher:Wiley
ISSN:2198-3844
Status:Published
Keywords:Band structure; Mg2Ge; Thermoelectric
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Transport
HGF - Program Themes:Road Transport
DLR - Research area:Transport
DLR - Program:V ST Straßenverkehr
DLR - Research theme (Project):V - NGC Antriebssystem und Energiemanagement
Location: Köln-Porz
Institutes and Institutions:Institute of Materials Research > Thermoelectric Materials and Systems
Deposited By: Frank, Adina
Deposited On:06 Nov 2020 10:21
Last Modified:06 Nov 2020 10:21

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