Thermoelectric properties and microstructure of Ba 8Al 14Si 31 and EuBa 7Al 13Si 33

Cathie L. Condron, Susan M. Kauzlarich, Franck Gascoin, G. Jeffery Snyder

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Abstract

Powder samples of the type I clathrate phases, with the proposed stoichiometry Ba 8Al 16Si 30 and Eu 2Ba 6Al 16Si 30, were synthesized using direct reaction of stoichiometric amounts of the elements. Rietveld refinement of powder X-ray diffraction data is consistent with the clathrate type I structure. Composition, microstructure, and thermoelectric property measurements were made on hot-pressed pellets. Stoichiometry of the Ba 8Al 16Si 30 sample was determined from microprobe data to be Ba 8Al 14Si 31, close to the deficient framework solid solution of the general formula, Ba 8Al xSi 42-3/4x[] 4-1/4x (x -14; [], open square indicates lattice defect). In the case of the rare-earth-substituted compound, microprobe analysis of the microstructure indicates that it is not single phase, but contains multiple components, most of the general clathrate stoichiometry. The majority phase has the stoichiometry EuBa 7Al 13Si 32. Both phases show conductivity typical of heavily doped semiconductors with negative Seebeck coefficients. The highest Seebeck coefficients are - 99 and -71 μV/K at 1192 K for Ba 8Al 14Si 31 and EuBa 7Al 13Si 33, respectively. The maximum zT is 0.34 at 1150 K and 0.22 at 1165 K for Ba 8Al 14Si 31 and EuBa 7Al 13Si 33, respectively.

Original languageEnglish (US)
Pages (from-to)4939-4945
Number of pages7
JournalChemistry of Materials
Volume18
Issue number20
DOIs
StatePublished - Oct 3 2006

ASJC Scopus subject areas

  • Materials Chemistry
  • Materials Science(all)

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    Condron, C. L., Kauzlarich, S. M., Gascoin, F., & Snyder, G. J. (2006). Thermoelectric properties and microstructure of Ba 8Al 14Si 31 and EuBa 7Al 13Si 33 Chemistry of Materials, 18(20), 4939-4945. https://doi.org/10.1021/cm061483u