Synthesis and Crystal Structure of Layered Oxyhalides BaPbBi_3Nb_2O_(11)X (X = Cl, Br, I)1

摘要

Three new bismuth oxyhalides BaPbBi_3Nb_2O_(11)X (X = Cl, Br, I), including the first perovskite bismuth oxyiodide, were prepared by ceramic route. Their crystal structure is formed by intergrowth of Sillen (PbBiO_2X) and Aurivillius (BaBi_2Nb_2O_9) phases. The results of Rietveld refinements show that the peculiarities of the building blocks (in particular, the distribution of Ba~(2+) and Bi~(3+)) remain intact upon formation of the intergrowth structure. The Ba~(2+) cations prefer pure-oxygen to mixed oxygen-halogen environment which can be explained on the basis of bond valence method.