Phase stability and chemical composition dependence of the thermoelectric properties of the type-I clathrate Ba{sub 8}Al{sub x}Si{sub 46-x} (8{<=}x{<=}15)

Journal Article · Sun May 15 00:00:00 EDT 2011 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2011.03.038· OSTI ID:21494282

Tsujii, Naohito ^[1]; Roudebush, John H ^[2]; Zevalkink, Alex ^[3]; Cox-Uvarov, Catherine A ^[2]; Jeffery Snyder, G ^[3]; Kauzlarich, Susan M ^[2]

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1. National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan)
2. Department of Chemistry, University of California, One Shields Avenue, Davis, CA 95616 (United States)
3. Materials Science, California Institute of Technology, 1200 California Blvd, Pasadena, CA 91125 (United States)

Phase stability of the type-I clathrate compound Ba{sub 8}Al{sub x}Si{sub 46-x} and the thermoelectric property dependence on chemical composition are presented. Polycrystalline samples were prepared by argon arc melting and annealing. Results of powder X-ray diffraction and electron microprobe analysis show that the type-I structure is formed without framework deficiency for 8{<=}x{<=}15. Lattice constant a increases linearly with the increase of x. Thermoelectric properties were measured for x=12, 14 and 15. The Seebeck coefficients are negative, with the absolute values increasing with x. The highest figure of merit zT=0.24 was observed for x=15 at T=1000 K, with carrier electron density n=3x10{sup 21} cm{sup -3}. A theoretical calculation based on the single parabolic band model reveals the optimum carrier concentration to be n{approx}4x10{sup 20} cm{sup -3}, where zT{approx}0.7 at T=1000 K is predicted. -- Graphical Abstract: Ba{sub 8}Al{sub x}Si{sub 46-x} is found to crystallize in the type-I clathrate structure without framework deficiency for 8{<=}x {<=}15. Thermoelectric figure of merit reaches zT=0.24 for x=15 at 1000 K, and calculation predicts zT{approx}0.7 for a lower carrier concentration. Display Omitted Highlights: {yields} Phase relation of the type-I clathrate Ba{sub 8}Al{sub x}Si{sub 46-x} is clarified. {yields} Thermoelectric performance becomes higher with the increase of Al content x. {yields} Low lattice thermal conductivity comparable to glasses is observed. {yields} Figure of merit zT=0.7 is predicted from calculation at the carrier concentration n{approx}4x10{sup 20} cm{sup -3}.

• OSTI ID: 21494282
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 5 Vol. 184; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
ANNEALING
ARGON
BARIUM COMPOUNDS
CHEMICAL ANALYSIS
CHEMICAL COMPOSITION
CLATHRATES
COHERENT SCATTERING
CRYSTALS
DIFFRACTION
ELECTRICAL PROPERTIES
ELECTRON DENSITY
ELECTRON MICROPROBE ANALYSIS
ELEMENTS
FLUIDS
GASES
GLASS
HEAT TREATMENTS
LATTICE PARAMETERS
MELTING
MICROANALYSIS
NONDESTRUCTIVE ANALYSIS
NONMETALS
PERFORMANCE
PHASE STABILITY
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
POLYCRYSTALS
RARE GASES
SCATTERING
SILICON COMPOUNDS
STABILITY
TEMPERATURE RANGE
TEMPERATURE RANGE 0400-1000 K
THERMAL CONDUCTIVITY
THERMODYNAMIC PROPERTIES
THERMOELECTRIC PROPERTIES
X-RAY DIFFRACTION