Über ein cadmiumreiches Orthovanadat Ba2,5Cd11(VO4)9 mit Cadmium in oktaedrischer und tetragonal pyramidaler Koordination / On a Cadmium Rich Orthovanadate Ba2,5Cd11(VO4)9 Showing Cadmium in Octahedral and Square Pyramidal Coordination

Abstract

Single crystals of Ba2,5Cd11(VO4)9 have been prepared by solid state reactions. The new compound crystallizes with orthorhombic symmetry, space group D142h-Pbcn, a = 20.842(6), b = 13.471(3), c = 11.838(9) Å, Z = 4. The crystal structure is characterized and dominated by CdO6 octahedra and unusual square pyramids of O2- around Cd2+ forming a three-dimensional [Cd11O36] network. The interstices are occupied by V5+ and Ba2+ ions. This results in VO4 tetrahedra and irregular BaO10 polyhedra isolated from each other. Occupation of the barium positions is deficient in agreement with the valence state V5+ and calculations of the coulomb terms of lattice energy.