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 language | English (US) |
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Pages (from-to) | 1176-1185 |
Number of pages | 10 |
Journal | Journal of Solid State Chemistry |
Volume | 184 |
Issue number | 5 |
DOIs | |
State | Published - 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
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Condensed Matter Physics
- Physical and Theoretical Chemistry
- Inorganic Chemistry
- Materials Chemistry