A Novel Family of Layered Bismuth Compounds: I. The Crystal Structures of Pb0.6Bi1.4Cs0.6O2Cl2 and Pb0.6Bi3.4Cs0.6O4Cl4

Twenty new multinary bismuth oxide halogenides have been prepared and characterized by means of X-ray powder diffraction. In their structures, fluorite-related layers are separated by CsClrelated metal–halogen sheets. Four compounds are isostructural to Ca3Bi5CsO8Cl6 which has an intergrowth structure between a Sillén X1 phase and a novel structural element ("Y2"). Another four compounds crystallize in a novel structure type which is an intergrowth between the X2 Sillén phase and the Y2 element. The remaining 12 compounds adopt the Y2 structure which is also a new structure type. In the former two families, Bi3+ can be substituted only by Pb2+; in the latter family, Bi3+ can also be substituted by Na+ and Ba2+. The crystal structure of Pb0.6Bi3.4Cs0.6O4Cl4 (intergrowth X2Y2 structure) has been solved from single crystal data, and the structure of Pb0.6Bi1.4Cs0.6O2Cl2 (Y2 structure) has been solved from powder data. Crystal chemical relationships to Sillén phases are discussed.