Crystal growth of uranium-containing complex oxides Ba2Na0 83U1 17O6, BaK4U3O12 and Na3Ca1 5UO6

Single crystals of complex uranium oxides Ba2Na0 83U1 17O6 BaK4U3O12 and Na3Ca1 5UO6 were grown out of reactive carbonate melts The crystal structures the three uranates were determined by single crystal X-ray diffraction Ba2Na0 83U1 O-17(6) crystallizes in the Fm (3) over barm space group a = 8 6173(1) with a disordered cubic double perovskite structure BaK4U3O12 forms in the cubic Im (3) over barm space group a = 8 7232(1) with the asymmetric unit consisting of three metal positions which shows improvement of the structure refinement from the published results Na3Ca1 5UO6 crystallizes in the orthorhombic Fddd space group with a = 6 6573(2) b = 9 6111(3) and c = 20 1155(5) in a rock salt superstructure In all three oxides the U (VI) canon is octahedrally coordinated While the UO6 octahedra in Ba2Na0 83U1 O-17(6) are undistorted due to oxygen disorder the UO6 octahedra in BaK4U3O12 and Na3Ca1 5UO6 feature the typical uranyl geometry with four long two short U-O bonds (C) 2010 Elsevier Masson SAS All rights reserved