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High-Temperature Thermoelectric Properties of the Solid−Solution Zintl Phase Eu_(11)Cd_6Sb_(12−x)As_x (x < 3)

Kazem, Nasrim and Xie, Weiwei and Ohno, Saneyuki and Zevalkink, Alexandra and Miller, Gordon J. and Snyder, G. Jeffrey and Kauzlarich, Susan M. (2014) High-Temperature Thermoelectric Properties of the Solid−Solution Zintl Phase Eu_(11)Cd_6Sb_(12−x)As_x (x < 3). Chemistry of Materials, 26 (3). pp. 1393-1403. ISSN 0897-4756. http://resolver.caltech.edu/CaltechAUTHORS:20140325-151014193

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Abstract

Zintl phases are compounds that have shown promise for thermoelectric applications. The title solid–solution Zintl compounds were prepared from the elements as single crystals using a tin flux for compositions x = 0, 1, 2, and 3. Eu_(11)Cd_6Sb_(12–x)As_x (x < 3) crystallize isostructurally in the centrosymmetric monoclinic space group C2/m (no. 12, Z = 2) as the Sr_(11)Cd_6Sb_(12) structure type (Pearson symbol mC58). Efforts to make the As compositions for x exceeding ~3 resulted in structures other than the Sr_(11)Cd_6Sb_(12) structure type. Single-crystal X-ray diffraction indicates that As does not randomly substitute for Sb in the structure but is site specific for each composition. The amount of As determined by structural refinement was verified by electron microprobe analysis. Electronic structures and energies calculated for various model structures of Eu_(11)Cd_6Sb_(10)As_2 (x = 2) indicated that the preferred As substitution pattern involves a mixture of three of the six pnicogen sites in the asymmetric unit. In addition, As substitution at the Pn4 site opens an energy gap at the Fermi level, whereas substitution at the other five pnicogen sites remains semimetallic with a pseudo gap. Thermoelectric properties of these compounds were measured on hot-pressed, fully densified pellets. Samples show exceptionally low lattice thermal conductivities from room temperature to 775 K: 0.78–0.49 W/mK for x = 0; 0.72–0.53 W/mK for x = 1; and 0.70–0.56 W/mK for x = 2. Eu_(11)Cd_6Sb_(12) shows a high p-type Seebeck coefficient (from +118 to 153 μ V/K) but also high electrical resistivity (6.8 to 12.8 mΩ·cm). The value of zT reaches 0.23 at 774 K. The properties of Eu_(11)Cd_6Sb_(12–x)As_x are interpreted in discussion with the As site substitution.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://pubs.acs.org/doi/abs/10.1021/cm403345aPublisherArticle
http://dx.doi.org/10.1021/cm403345aDOIArticle
ORCID:
AuthorORCID
Snyder, G. Jeffrey0000-0003-1414-8682
Additional Information:© 2014 American Chemical Society. Received: October 10, 2013. Revised: January 5, 2014. Published: January 6, 2014. We thank Prof. Marilyn Olmstead for assistance with crystallography, Dr. Sarah Roeske for assistance with microprobe analysis, Dr. Catherine Uvarov at Romny Scientific Inc. for assistance with the hot press, and Dr. Oliver Janka for many helpful discussions. This research was funded by GAANN fellowship and NSF DMR-1100313. Use of the Advanced Photon Source was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. Research carried out at the Ames Laboratory was supported by the U.S. Department of Energy, Office of Basic Energy Science, Division of Materials Sciences and Engineering. The Ames Laboratory is operated for the U.S. Department of Energy by Iowa State University under Contract No. DE-AC02-07CH11358.
Funders:
Funding AgencyGrant Number
GAANN fellowshipUNSPECIFIED
NSFDMR-1100313
Department of Energy (DOE)DE-AC02-06CH11357
Department of Energy (DOE)DE-AC02-07CH11358
Record Number:CaltechAUTHORS:20140325-151014193
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20140325-151014193
Official Citation:High-Temperature Thermoelectric Properties of the Solid–Solution Zintl Phase Eu11Cd6Sb12–xAsx (x < 3) Nasrin Kazem, Weiwei Xie, Saneyuki Ohno, Alexandra Zevalkink, Gordon J. Miller, G. Jeffrey Snyder, and Susan M. Kauzlarich Chemistry of Materials 2014 26 (3), 1393-1403
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:44512
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:26 Mar 2014 20:32
Last Modified:18 Nov 2016 17:26

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