title: Synthesis, Characterization, and Low Temperature Transport Properties of Eu11-xYbxCd6Sb12Solid-Solution Zintl Phases.
abstract: Eu11-xYbxCd6Sb12Zintl solid solutions have been prepared by tin flux reaction by employing the elements Eu/Yb/Cd/Sb/Sn in the ratio 11 - xp:xp:6:12:30, where xpis an integer less than 11 representing the preparative amount of Eu (11 - xp) and Yb (xp). Efforts to make the Yb compositions for x exceeding ∼3 resulted in structures other than the Sr11Cd6Sb12structure type. The crystal structures and compositions were determined by single-crystal and powder X-ray diffraction and wavelength-dispersive X-ray analysis measurements. The title solid-solution Zintl compounds crystallize in the centrosymmetric monoclinic space group C2/m (no. 12, Z = 2) as the Sr11Cd6Sb12structure type (Pearson symbol mC58), and the lattice parameters decrease with increasing ytterbium content. Single crystal X-ray diffraction shows that Yb atoms are not randomly distributed in the Eu sites but have a site preference which can be attributed to size effects. The influence of the rare earth (RE) metal sites on thermal and electronic properties of RE11Cd6Sb12solid solutions has been studied by measuring their thermoelectric properties from 5 to 300 K after consolidation by either spark plasma sintering (SPS) or hot pressing (HP). Electron microprobe analysis reveals that some of the rare earth metal is lost during SPS; as a result pellets formed through SPS have lower electrical resistivity by an order of magnitude due to increased hole-charge carrier concentrations. While the carrier concentration increases, the mobility decreases due to deficiencies in Eu content. Refinement of powder X-ray diffraction shows that Eu loss is mainly from the Eu1 crystallographic site, which has a unique coordination suggesting that this site plays a key role in the transport properties of RE11Cd6Sb12.
authors.affiliation: Department of Chemistry, University of California , One Shields Ave., Davis, California 95616, United States.
authors.forename: Nasrin
authors.initials: N
authors.lastname: Kazem
authors.affiliation: Department of Chemistry, University of California , One Shields Ave., Davis, California 95616, United States.
authors.forename: Joya
authors.initials: J
authors.lastname: Cooley
authors.affiliation: Department of Physics, University of California , One Shields Ave., Davis, California 95616, United States.
authors.forename: Edward C
authors.initials: EC
authors.lastname: Burks
authors.affiliation: Department of Physics, University of California , One Shields Ave., Davis, California 95616, United States.
authors.forename: Kai
authors.initials: K
authors.lastname: Liu
authors.affiliation: Department of Chemistry, University of California , One Shields Ave., Davis, California 95616, United States.
authors.forename: Susan M
authors.initials: SM
authors.lastname: Kauzlarich