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 Ba2+ 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 Zr4+ 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 degrees 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.