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Crystal Structure, Characterization and Thermoelectric Properties of the Type-I Clathrate Ba_(8-y)Sr_yAl_(14)Si_(32) (0.6 ≤ y ≤ 1.3) Prepared by Aluminum Flux

Roudebush, John H. and Toberer, Eric S. and Hope, Håkon and Snyder, G. Jeffrey and Kauzlarich, Susan M. (2011) Crystal Structure, Characterization and Thermoelectric Properties of the Type-I Clathrate Ba_(8-y)Sr_yAl_(14)Si_(32) (0.6 ≤ y ≤ 1.3) Prepared by Aluminum Flux. Journal of Solid State Chemistry, 184 (5). pp. 1176-1185. ISSN 0022-4596.

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The title compound was prepared as single crystals using an aluminum flux technique. Single crystal and powder X-ray diffraction indicate that this composition crystallizes in the clathrate type-I structure, space group Pm3̄n. Electron microprobe characterization indicates the composition to be Ba_(8−y)Sr_yAl_(14.2(2))Si_(31.8(2)) (0.77<y<1.3). Single-crystal X-ray diffraction data (90 and 12 K) were refined with the Al content fixed at the microprobe value (12 K data: R_1=0.0233, wR_2=0.0441) on a crystal of compositions Ba. The Sr atom preferentially occupies the 2a position; mixed Al/Si occupancy was found on all framework sites. These refinements are consistent with a fully occupied framework and nearly fully occupied cation guest sites as found by microprobe analysis. Temperature dependent electrical resistivity and thermal conductivity have been measured from room temperature to 1200 K on a hot-pressed pellet. Electrical resistivity reveals metallic behavior. The negative Seebeck coefficient indicates transport processes dominated by electrons as carriers. Thermal conductivity is between 22 and 25 mW/cm K. The sample shows n-type conductivity with a maximum figure of merit, zT of 0.3 at 1200 K. A single parabolic band model predicts a five-fold increase in zT at 800 K if carrier concentration is lowered.

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Additional Information:© 2011 Elsevier Inc. Received 11 December 2010; revised 18 February 2011; accepted 27 February 2011. Available online 8 March 2011. We gratefully acknowledge the financial support from NSF DMR0600742 and NASA Jet Propulsion Laboratory. We thank Cathie Condron for her early contributions to the research.
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Subject Keywords:Thermoelectric properties; Zintl phase; Low temperature X-ray diffraction; 12 K structure; Inorganic clathrate; Ba8Al16Si30; Clathrate type-I
Issue or Number:5
Record Number:CaltechAUTHORS:20110608-081329151
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Official Citation:John H. Roudebush, Eric S. Toberer, Hakon Hope, G. Jeffrey Snyder, Susan M. Kauzlarich, Crystal structure, characterization and thermoelectric properties of the type-I clathrate Ba8-ySryAl14Si32 (0.6<=y<=1.3) prepared by aluminum flux, Journal of Solid State Chemistry, Volume 184, Issue 5, May 2011, Pages 1176-1185, ISSN 0022-4596, DOI: 10.1016/j.jssc.2011.02.027. (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:23939
Deposited By: Ruth Sustaita
Deposited On:08 Jun 2011 18:05
Last Modified:03 Oct 2019 02:51

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