Synthesis and structure determination of In3TeO3F7: An indium oxyfluorotellurate IV derived from W bronze structure with Te4+ in hexagonal tunnels

After InTeO3F and InTe2O5F recently described, a new compound In3TeO3F7 is characterized in the In-Te-IV-O-F system. The crystal structure was determined by single X-ray diffraction and refined to R-1=0.028. In3TeO3F7 crystallizes in orthorhombic space group Cmmm, a = 7.850(2)angstrom, b = 27.637(6)angstrom, c = 4.098(1)angstrom, V = 889.1(4)angstrom(3) and Z = 4. Its structure consists of the stacking, via vertices, of identical layers composed of InF6 and InO2F4 octahedra sharing corners and of InO4F3 pentagonal bipyramids sharing edges and vertices. The Te cations statistically occupy one or the other of two close sites located inside tunnels delimited by the In polyhedra and are bonded to F anions located in the same tunnels. The structure can be considered as an intergrowth of parallel strips of MIn3F10 and hexagonal tungsten bronze (c)-types. It is compared to other structures such as the bronze Sb0.157WO3, TeMo5O16 and Sb2Mo10O31, phases also comprising Te4+ or Sb3+ inside hexagonal tunnels. The electronic lone pair of Te4+ is stereochemically active and a perfect O/F ordering occurs on the anionic sites. (C) 2010 Elsevier B.V. All rights reserved.