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  Nonstoichiometry and chemical purity effects in thermoelectric Ba8Ga16Ge30 clathrate

Bryan, J. D., Blake, N. P., Metiu, H., Stucky, G. D., Iversen, B. B., Poulsen, R. D., et al. (2002). Nonstoichiometry and chemical purity effects in thermoelectric Ba8Ga16Ge30 clathrate. Journal of Applied Physics, 92(12), 7281-7290. doi:10.1063/1.1519334.

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Item Permalink: http://hdl.handle.net/11858/00-001M-0000-0015-30C0-F Version Permalink: http://hdl.handle.net/11858/00-001M-0000-0017-D5EB-4
Genre: Journal Article

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Bryan, J. D., Author
Blake, N. P., Author
Metiu, H., Author
Stucky, G. D., Author
Iversen, B. B., Author
Poulsen, R. D., Author
Bentien, A.1, Author              
Affiliations:
1Max Planck Institute for Chemical Physics of Solids, Max Planck Society, ou_1863404              

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 Abstract: Zone melting purification experiments have been carried out on the clathrate, Ba8Ga16Ge30. The impurities present have been identified and their approximate concentrations measured. Trace impurities were determined to be approximately 240 parts per million (ppm) in the most impure sample to 17 ppm in the most pure sample. The temperature-dependent Seebeck coefficient, thermal conductivity, and electrical conductivity are reported as a function of sample purity as well as the room-temperature Hall coefficient. Microprobe analysis suggests that the samples are nonstoichiometric with excess Ge relative to Ga, and there are indications of the presence of defects. Single-crystal x- ray investigations as well as synchrotron powder diffraction measurements support the presence of defects, but the x-ray data cannot accurately determine the relative amounts of Ga and Ge. Band-structure calculations in the generalized gradient approximation show that the measured Hall and Seebeck coefficients are consistent with a defect lattice of approximate stoichiometry Ba8Ga14Ge31. Although the figure of merit (ZT) is found to be the highest for the purest sample, the dominant contribution to transport is conjectured to arise from deviations from the ideal stoichiometry and not impurities. (C) 2002 American Institute of Physics.

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Language(s): eng - English
 Dates: 2002-12-15
 Publication Status: Published in print
 Pages: -
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 Table of Contents: -
 Rev. Method: Peer
 Identifiers: eDoc: 16444
ISI: 000179495100050
DOI: 10.1063/1.1519334
 Degree: -

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Title: Journal of Applied Physics
  Alternative Title : J. Appl. Phys.
Source Genre: Journal
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Pages: - Volume / Issue: 92 (12) Sequence Number: - Start / End Page: 7281 - 7290 Identifier: ISSN: 0021-8979