Crystal structure, characterization and thermoelectric properties of the type-I clathrate Ba8-ySryAl14Si32 (0.6≤y≤1.3) prepared by aluminum flux

John H. Roudebush, Eric S. Toberer, Håkon Hope, G. Jeffrey Snyder, Susan M. Kauzlarich

Research output: Contribution to journalArticle

24 Scopus citations

Abstract

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 Pm3n. Electron microprobe characterization indicates the composition to be Ba 8-ySryAl14.2(2)Si31.8(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, wR2=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.

Original languageEnglish (US)
Pages (from-to)1176-1185
Number of pages10
JournalJournal of Solid State Chemistry
Volume184
Issue number5
DOIs
StatePublished - May 2011

Keywords

  • 12 K structure
  • BaAlSi
  • Clathrate type-I
  • Inorganic clathrate
  • Low temperature X-ray diffraction
  • Thermoelectric properties
  • Zintl phase

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Inorganic Chemistry
  • Physical and Theoretical Chemistry
  • Ceramics and Composites
  • Electronic, Optical and Magnetic Materials
  • Materials Chemistry

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