TY - JOUR
T1 - Thermoelectric properties and microstructure of Ba 8Al 14Si 31 and EuBa 7Al 13Si 33
AU - Condron, Cathie L.
AU - Kauzlarich, Susan M.
AU - Gascoin, Franck
AU - Snyder, G. Jeffery
PY - 2006/10/3
Y1 - 2006/10/3
N2 - 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.
AB - 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.
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U2 - 10.1021/cm061483u
DO - 10.1021/cm061483u
M3 - Article
AN - SCOPUS:33750304834
SN - 0897-4756
VL - 18
SP - 4939
EP - 4945
JO - Chemistry of Materials
JF - Chemistry of Materials
IS - 20
ER -