title: Two new types of oxyfluorotellurates(IV): ScTeO3F and InTeO3F.
abstract: In the course of a general study of oxyfluorotellurates(IV), materials likely to exhibit interesting nonlinear optical properties, the crystal structures of the new phases scandium tellurium trioxide fluoride, ScTeO(3)F, and indium tellurium trioxide fluoride, InTeO(3)F, belonging to two different structural types and also differing from that of the recently published MTeO(3)F (M = Fe, Ga and Cr) series, have been determined. The ScTeO(3)F structure can be described as an intergrowth of two different layers of scandium octahedra connected via isolated TeO(3) groups. The scandium ions occupy two different sites with ..2 and 2.. site symmetry. The Te, F and O atoms are on general positions of the Pnna space group. The InTeO(3)F structure consists of zigzag sheets of InO(5)F octahedra. The In, Te, O and F atoms are all located on general positions of the P2(1)/a space group. TeO(3)F polyhedra are inserted between the zigzag sheets of InO(5)F octahedra and with them form double (InTeO(3)F)(n) layers. Therefore, InTeO(3)F is a true layer structure, unlike the previous types. In all these phases, the electronic lone pair of the Te(IV) atom is stereochemically active and a full O/F anionic ordering is observed.
authors.affiliation: Science des Procédés Céramiques et de Traitements de Surface, UMR-CNRS 6638, Université de Limoges, Faculté des Sciences et Techniques, 123 Avenue A. Thomas, Limoges 87060, France.
authors.forename: Nefla
authors.initials: N
authors.lastname: Jennene Boukharrata
authors.forename: Jean Paul
authors.initials: JP
authors.lastname: Laval
authors.forename: Philippe
authors.initials: P
authors.lastname: Thomas