Synthesis and crystal structure of layered oxyhalides BaPbBi3Nb2O11X (X = Cl, Br, I)

Three new bismuth oxyhalides BaPbBi 3 Nb 2 O 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 Sillén (PbBiO 2 X) and Aurivillius (BaBi 2 Nb 2 O 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.