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Title: Concurrent La and A-site vacancy doping modulates the thermoelectric response of SrTiO3: experimental and computational evidence
Authors: Azough, Feridoon
Jackson, Samuel S.
Ekren, Dursun
Freer, Robert
Molinari, Marco
Yeandel, Stephen R.
Panchmatia, Pooja M.
Parker, Stephen C.
Hernandez Maldonado, David
Kepaptsoglou, Demie M.
Ramasse, Quentin M.
Keywords: Molecular dynamics
Strontium titanate
Thermal conductivity
Vacancy−cation ordering
Issue Date: 2017
Publisher: © American Chemical Society
Citation: AZOUGH, F. ... et al, 2017. Concurrent La and A-site vacancy doping modulates the thermoelectric response of SrTiO3: experimental and computational evidence. ACS Applied Materials and Interfaces, 9 (48), pp. 41988–42000.
Abstract: To help understand the factors controlling the performance of one of the most promising n-type oxide thermoelectric SrTiO3, we need to explore structural control at the atomic level. In Sr1–xLa2x/3TiO3 ceramics (0.0 ≤ x ≤ 0.9), we determined that the thermal conductivity can be reduced and controlled through an interplay of La-substitution and A-site vacancies and the formation of a layered structure. The decrease in thermal conductivity with La and A-site vacancy substitution dominates the trend in the overall thermoelectric response. The maximum dimensionless figure of merit is 0.27 at 1070 K for composition x = 0.50 where half of the A-sites are occupied with La and vacancies. Atomic resolution Z-contrast imaging and atomic scale chemical analysis show that as the La content increases, A-site vacancies initially distribute randomly (x < 0.3), then cluster (x ≈ 0.5), and finally form layers (x = 0.9). The layering is accompanied by a structural phase transformation from cubic to orthorhombic and the formation of 90° rotational twins and antiphase boundaries, leading to the formation of localized supercells. The distribution of La and A-site vacancies contributes to a nonuniform distribution of atomic scale features. This combination induces temperature stable behavior in the material and reduces thermal conductivity, an important route to enhancement of the thermoelectric performance. A computational study confirmed that the thermal conductivity of SrTiO3 is lowered by the introduction of La and A-site vacancies as shown by the experiments. The modeling supports that a critical mass of A-site vacancies is needed to reduce thermal conductivity and that the arrangement of La, Sr, and A-site vacancies has a significant impact on thermal conductivity only at high La concentration.
Description: This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Applied Materials and Interfaces, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acsami.7b14231.
Sponsor: The authors gratefully acknowledge the support and the provision of funding from EPSRC for this work (EP/H043462, EP/I036230/1, EP/L014068/1, EP/L017695/1, EP/I03601X/1, and EP/K016288/1).
Version: Accepted for publication
DOI: 10.1021/acsami.7b14231
URI: https://dspace.lboro.ac.uk/2134/27914
Publisher Link: https://doi.org/10.1021/acsami.7b14231
ISSN: 1944-8244
Appears in Collections:Published Articles (Chemistry)

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