Article (Scientific journals)
On the True Indium Content of In-Filled Skutterudites
Visnow, E.; Heinrich, C. P.; Schmitz, A. et al.
2015In Inorganic Chemistry, 54 (16), p. 7818-7827
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Abstract :
[en] The incongruently melting single-filled skutterudite In<inf>x</inf>Co<inf>4</inf>Sb<inf>12</inf> is known as a promising bulk thermoelectric material. However, the products of current bulk syntheses contain always impurities of InSb, Sb, CoSb, or CoSb<inf>2</inf>, which prevent an unbiased determination of its thermoelectric properties. We report a new two-step synthesis of high-purity In<inf>x</inf>Co<inf>4</inf>Sb<inf>12</inf> with nominal compositions x = 0.12, 0.15, 0.18, and 0.20 that separates the kieftite (CoSb<inf>3</inf>) formation from the topotactic filler insertion. This approach allows conducting the reactions at lower temperatures with shorter reaction times and circumventing the formation of impurity phases. The synthesis can be extended to other filled skutterudites. High-density (>98%) pellets for thermoelectric characterization were prepared by current-assisted short-time sintering. Sample homogeneity was demonstrated by potential and Seebeck microprobe measurements of the complete pellet surfaces. Synchrotron X-ray diffraction showed a purity of 99.9% product with traces (≤0.1%) of InSb in samples of nominal composition In<inf>0.18</inf>Co<inf>4</inf>Sb<inf>12</inf> and In<inf>0.20</inf>Co<inf>4</inf>Sb<inf>12</inf>. Rietveld refinements revealed a linear correlation between the true In occupancy and the lattice parameter a. This allows the determination of the true In filling in skutterudites and predicting the In content of unknown A<inf>x</inf>Co<inf>4</inf>Sb<inf>12</inf>. The high purity of In<inf>x</inf>Co<inf>4</inf>Sb<inf>12</inf> allowed studying the transport properties without bias from side phases. A figure of merit close to unity at 420 °C was obtained for a sample of a true composition of In<inf>0.160(2)</inf>Co<inf>4</inf>Sb<inf>12</inf> (nominal composition In<inf>0.18</inf>Co<inf>4</inf>Sb<inf>12</inf>). The lower degree of In filling has a dramatic effect on the thermoelectric properties as demonstrated by the sample of nominal composition In<inf>0.20</inf>Co<inf>4</inf>Sb<inf>12</inf>. The presence of InSb in amounts of ∼0.1 vol% led to a substantially lower degree of interstitial site filling of 0.144, and the figure of merit zT decreased by 18%, which demonstrates the significance of the true filler atom content in skutterudite materials. (Graph Presented). © 2015 American Chemical Society.
Disciplines :
Chemistry
Author, co-author :
Visnow, E.;  Institut für Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universität, Duesbergweg 10-14, Mainz, Germany
Heinrich, C. P.;  Institut für Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universität, Duesbergweg 10-14, Mainz, Germany, Graduate School Materials Science in Mainz, Johannes Gutenberg-Universität, Staudinger Weg 9, Mainz, Germany
Schmitz, A.;  Deutsches Zentrum für Luft- und Raumfahrt E.V. (DLR), Institut für Werkstoff-Forschung, Linder Höhe, Köln, Germany
De Boor, J.;  Deutsches Zentrum für Luft- und Raumfahrt E.V. (DLR), Institut für Werkstoff-Forschung, Linder Höhe, Köln, Germany
Leidich, P.;  Institut für Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universität, Duesbergweg 10-14, Mainz, Germany
Klobes, B.;  Jülich Centre for Neutron Science JCNS, Peter Grünberg Institute PGI, Forschungszentrum Jülich GmbH, Jülich, Germany
Hermann, Raphaël ;  Université de Liège - ULiège > Département de chimie (sciences) > Département de chimie (sciences)
Müller, W. E.;  Deutsches Zentrum für Luft- und Raumfahrt E.V. (DLR), Institut für Werkstoff-Forschung, Linder Höhe, Köln, Germany, Institute of Inorganic and Analytical Chemistry, Justus Liebig University Giessen, Heinrich-Buff-Ring 58, Giessen, Germany
Tremel, W.;  Institut für Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universität, Duesbergweg 10-14, Mainz, Germany
Language :
English
Title :
On the True Indium Content of In-Filled Skutterudites
Publication date :
2015
Journal title :
Inorganic Chemistry
ISSN :
0020-1669
eISSN :
1520-510X
Publisher :
American Chemical Society
Volume :
54
Issue :
16
Pages :
7818-7827
Peer reviewed :
Peer Reviewed verified by ORBi
Name of the research project :
DFG priority program SPP1386 “Nanostructured Thermoelectrics”
Funders :
DFG - Deutsche Forschungsgemeinschaft [DE]
DOE - United States. Department of Energy [US-OR]
Available on ORBi :
since 14 November 2020

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