New cobaltite materials containing CdI2-type layers: Synthesis and structures of Ba2Co4ClO7 and Ba2Co4BrO7
نویسندگان
چکیده
Single crystals of the title compounds were prepared by solid-solid reaction using BaCl2 or BaBr2 flux at 1100°C. The structures of these two new cobaltites were solved and refined in the trigonal symmetry with space group R3 m: a=5.716(2) Å, c=45.01(3) Å for Ba2Co4ClO7 and a=5.7434(5) Å, c=46.151(9) Å for Ba2Co4BrO7. The two compounds are isostructural and their structures can be considered as the intergrowth along [001] of hexagonal blocks (Ba2Co8O14) 2built from a close-packing of [O4] and [BaO3] layers with octahedral and tetrahedral cobalt, separated by fluorite-type double layers (Ba2Cl2) 2+ or (Ba2Br2) . The main difference between Ba2Co4ClO7 and Ba2Co4BrO7 is due to the fluoritetype layers: (Ba2Cl2) 2+ double layers are perfectly ordered while (Ba2Br2) 2+ blocks are affected by a structural disorder through the bromine atoms.
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