title: Crystal Growth, Structures, and Properties of the Complex Borides, LaOs2Al2B and La2Os2AlB2.
abstract: Single crystals of two novel quaternary metal borides, LaOs2Al2B and La2Os2AlB2, have been grown from La/Ni eutectic fluxes. LaOs2Al2B crystallizes in tetragonal space group P4/mmm with the CeCr2Si2C-type structure, and lattice parameters a = 4.2075(6) Å and c = 5.634(1) Å. La2Os2AlB2 exhibits a new crystal structure in monoclinic space group C2/c with lattice parameters a = 16.629(3) Å, b = 6.048(1) Å, c = 10.393(2) Å, and β = 113.96(3)°. Both structures are three-dimensional frameworks with unusual coordination (for solid-state compounds) of the boron atoms by transition metal atoms. The boron atom is square planar in LaOs2Al2B, whereas it exhibits linear and T-shaped geometries in La2Os2AlB2. Electrical resistivity measurements reveal poor metal behavior (ρ300 K ∼ 900 μΩ cm) for La2Os2AlB2, consistent with the electronic band structure calculations, which also predict a metallic character for LaOs2Al2B.
authors.affiliation: †Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States.
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Bugaris
authors.affiliation: †Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States.
authors.forename: Fei
authors.initials: F
authors.lastname: Han
authors.affiliation: ‡Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, United States.|§Advanced Material Division, Korea Research Institute of Chemical Technology, Daejeon 305-600, Korea.
authors.forename: Jino
authors.initials: J
authors.lastname: Im
authors.affiliation: †Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States.
authors.forename: Duck Young
authors.initials: DY
authors.lastname: Chung
authors.affiliation: ‡Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, United States.
authors.forename: Arthur J
authors.initials: AJ
authors.lastname: Freeman
authors.affiliation: †Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States.|∥Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States.
authors.forename: Mercouri G
authors.initials: MG
authors.lastname: Kanatzidis