title: Dimensionality variations in new zirconium iodates: hydrothermal syntheses, structural determination, and characterization of BaZr(IO₃)₆ and K₂Zr(IO₃)₆.
abstract: Two new quaternary zirconium iodates, BaZr(IO3)6 and K2Zr(IO3)6, have been synthesized through hydrothermal reactions using BaCO3 (or K2CO3), ZrO2, and HIO3 as reagents. Single crystal and powder X-ray diffraction were used to determine crystal structures of the compounds. BaZr(IO3)6 exhibits infinite bands that are composed of ZrO7 pentagonal bipyramids and IO3 trigonal pyramids, in which Ba(2+) cations are sandwiched by the bands. K2Zr(IO3)6 exhibits a molecular structure that is composed of ZrO6 octahedra and IO3 groups. The dimensionality variations seem to be attributable to the flexible coordination numbers of Zr(4+) cations with large ionic radii as well as the number of counter cations. Both of the materials are thermally stable up to approximately 440-450 °C and decompose to the corresponding metal zirconium oxides above these temperatures. The band gaps for BaZr(IO3)6 and K2Zr(IO3)6 are calculated to be 3.1 and 3.0 eV, respectively, using the (K/S)-versus-E plots obtained from the UV-vis diffuse reflectance spectra. Infrared spectra and local dipole moment calculations are also presented.
authors.affiliation: Department of Chemistry, Chung-Ang University, Seoul, 156-756, Republic of Korea. kmok@cau.ac.kr.
authors.forename: Hyun Sun
authors.initials: HS
authors.lastname: Ahn
authors.forename: Dong Woo
authors.initials: DW
authors.lastname: Lee
authors.forename: Kang Min
authors.initials: KM
authors.lastname: Ok