Abstract
Two new pentavalent bismuthates, CaBi2O6−x·1.1H2O and PbBi2O6−x·H2O were prepared from NaBiO3·nH2O. Broadened X-ray powder diffraction patterns for both bismuthates were indexed to the hexagonal cell observed for PbSb2O6-type SrBi2O6. The lattice parameters were a = 0.555(1) and c = 0.530(1) nm for CaBi2O6−x·1.1H2O and a = 0.5544(4) and c = 0.531(1) nm for PbBi2O6−x·H2O. At elevated temperatures, the Ca derivative decomposed to Ca3Bi8O15 and an unknown phase via the fluorite-type structure, whereas the Pb derivative changed to Pb1/3Bi2/3O4/3 via the fluorite-type (Pb1/3Bi2/3)O1.4. Both Ca and Pb derivatives exhibited photocatalytic activity for the decomposition of phenol under visible light irradiation, although the adsorption of phenol was observed under dark conditions. The fluorite-type phases evolved from the Ca and Pb derivatives did not adsorb phenol under dark conditions, and their photocatalytic activities toward phenol decomposition under visible light were inferior to those of the parent compounds.
