Crystal Growth, Structures, and Properties of the Complex Borides, LaOs2Al2B and La2Os2AlB2
文摘
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) 脜 and c = 5.634(1) 脜. La2Os2AlB2 exhibits a new crystal structure in monoclinic space group C2/c with lattice parameters a = 16.629(3) 脜, b = 6.048(1) 脜, c = 10.393(2) 脜, and 尾 = 113.96(3)掳. 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 (蟻300聽K 鈭?900 渭惟 cm) for La2Os2AlB2, consistent with the electronic band structure calculations, which also predict a metallic character for LaOs2Al2B.