title: Structure and thermoelectric characterization of Ba8Al14Si31.
abstract: A molten Al flux method was used to grow single crystals of the type I clathrate compound Ba8Al14Si31. Single-crystal neutron diffraction data for Ba8Al14Si31 were collected at room temperature using the SCD instrument at the Intense Pulsed Neutron Source, Argonne National Laboratory. Single-crystal neutron diffraction of Ba8Al14Si31 confirms that the Al partially occupies all of the framework sites (R1 = 0.0435, wR2 = 0.0687). Stoichiometry was determined by electron microprobe analysis, density measurements, and neutron diffraction analysis. Solid-state (27)Al NMR provides additional evidence for site preferences within the framework. This phase is best described as a framework-deficient solid solution Ba8Al14Si31, with the general formula, Ba(8)Al(x)Si(42-3/4x)[](4-1/4x) ([] indicates lattice defects). DSC measurements and powder X-ray diffraction data indicate that this is a congruently melting phase at 1416 K. Temperature-dependent resistivity reveals metallic behavior. The negative Seebeck coefficient indicates transport processes dominated by electrons as carriers.
authors.affiliation: Department of Chemistry, University of California, One Shields Avenue, Davis, California 95616, USA.
authors.forename: Cathie L
authors.initials: CL
authors.lastname: Condron
authors.forename: J
authors.initials: J
authors.lastname: Martin
authors.forename: G S
authors.initials: GS
authors.lastname: Nolas
authors.forename: Paula M B
authors.initials: PM
authors.lastname: Piccoli
authors.forename: Arthur J
authors.initials: AJ
authors.lastname: Schultz
authors.forename: Susan M
authors.initials: SM
authors.lastname: Kauzlarich