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On the Relevance of Defects for the Selection of Contacting Electrodes: Ag as an Example for Mg2(Si,Sn)-based Thermoelectric Generators

Ayachi, Sahar and Deshpande, Radhika and Ponnusamy, Prasanna and Park, Sungjin and Ryu, Byungki and Müller, Eckhard and de Boor, Johannes (2020) On the Relevance of Defects for the Selection of Contacting Electrodes: Ag as an Example for Mg2(Si,Sn)-based Thermoelectric Generators. Materials Today Physics. Elsevier. doi: 10.1016/j.mtphys.2020.100309. ISSN 2542-5293.

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Abstract

In developing thermoelectric generators, optimizing interfaces between thermoelectric materials and contacting electrodes is a crucial step. Among the tested electrodes for Mg2(Si,Sn)-based generators, Ag shows good adhesion, controllable interfaces and low electrical contact resistances. However, it induces unexpected changes in the Seebeck coefficient of n-type samples, while no change is observed in p-type. In order to understand said behavior, contacting results for Bi-doped Mg2Si, Mg2Sn and Mg2Si1-xSnx with Ag are compared with predictions based on defect formation energies obtained within hybrid-density functional theory (DFT). A qualitative description of the Ag diffusion mechanism in Mg2X is also introduced. Calculation results show that Ag-induced defects have sufficiently low formation energies to influence charge carrier concentrations, particularly Ag substitution on the Mg site (AgMg). AgMg acts as an acceptor and causes a counter-doping effect by compensating the electrons provided by Bi. However, in Li-doped p-type, as Li-defects have the lowest formation energies, a negligible charge carrier concentration change is predicted, which fits with experimental observations. Concerning solid solutions, interpolation from the binaries predicts a similar behavior, which also meets experimental findings. Therefore, this work not only establishes the calculation method and explains the observed effect, but also proves the importance of defects in selecting contacting electrodes.

Item URL in elib:https://elib.dlr.de/137155/
Document Type:Article
Title:On the Relevance of Defects for the Selection of Contacting Electrodes: Ag as an Example for Mg2(Si,Sn)-based Thermoelectric Generators
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Ayachi, SaharGerman aerospace center, institute of materials research, köln, germanyUNSPECIFIED
Deshpande, RadhikaGerman aerospace center, institute of materials research, köln, germanyUNSPECIFIED
Ponnusamy, Prasannagerman aerospace center, institute of materials research, köln, germanyUNSPECIFIED
Park, SungjinEnergy Conversion Research Center, Electrical Materials Research Division, Korea Electrotechnology Research Institute (KERI), Changwon, KoreaUNSPECIFIED
Ryu, ByungkiEnergy Conversion Research Center, Electrical Materials Research Division, Korea Electrotechnology Research Institute (KERI), Changwon, KoreaUNSPECIFIED
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:31 October 2020
Journal or Publication Title:Materials Today Physics
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
DOI :10.1016/j.mtphys.2020.100309
Publisher:Elsevier
ISSN:2542-5293
Status:Published
Keywords:Defects; Contacting electrodes; Ag, Mg2(Si,Sn), Thermoelectric
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space System Technology
DLR - Research area:Raumfahrt
DLR - Program:R SY - Space System Technology
DLR - Research theme (Project):R - Systemtechnologien (old)
Location: Köln-Porz
Institutes and Institutions:Institute of Materials Research > Thermoelectric Materials and Systems
Deposited By: Frank, Adina
Deposited On:06 Nov 2020 10:23
Last Modified:06 Nov 2020 10:23

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