A novel family of layered bismuth compounds, I. The crystal structures of Pb_0.6Bi_1.4Cs_0.6O₂Cl₂ and Pb_0.6Bi_3.4Cs_0.6O₄Cl₄

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 CsCl-related metal-halogen sheets. Four compounds are isostructural to Ca3Bi5CsO8Cl6 which has an intergrowth structure between a Sillen XI phase and a novel structural element ("Y2"). Another four compounds crystallize in a novel structure type which is an intergrowth between the X2 Sillen 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 pb(2+); in the latter family, Bi3+ can also be substituted by Na+ and Ba2+. The crystal structure of Pb0.6Bi3.4Cs0.6Cl4 (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 Sillen phases are discussed, (C) 1999 Academic Press.