SYNTHESIS AND CRYSTAL-STRUCTURE OF BATIOF4

The crystal structure of BaTiOF4 has been determined by X-Ray diffraction data from a single crystal grown by hydrothermal synthesis. The symmetry is orthorhombic: Pbcm, Z = 4, a = 5.1719(2) angstrom, b = 13.7555(7) angstrom, c = 5.5178(2) angstrom (R = 0.0264 and R(w) = 0.0313 for 1030 independent reflections). The structure, characterized by infinite kinked chains of cis connected TiO2F4 octahedra, running along [001], is also described in terms of stacking of quasi hexagonal compact planes of Ba2+, O2- and F- ions. Ba atoms, located in a classical cubooctahedral coordination (12), connect the chains to one another. The location of the O2- anions is discussed using the bond valence method. This structure is compared to those of the A(II)M(III)F5 compounds (BaGaF5, BaAlF5, BaMnF5, SrNiF5).