Incommensurate crystallographic shear structure of Ba_xBi _2-2xTi_4-xO_11-4x (X = 0.275)

The title compound generates diffraction patterns which are indexable within the framework of the higher-dimensional description of incommensurate structures. However, it is difficult to discriminate the main reflections from the satellite ones. This paper has clarified that the structure can be treated as a strongly modulated structure with sawtooth-like modulation functions and is classified as an incommensurate crystallographic shear (CS) structure. The structure consists of domains isostructural to β-Bi₂Ti ₄O₁₁ and domain boundaries composed of TiO₆ octahedra. Ba and Bi ions are accommodated in the cavities between TiO ₆ octahedra in the domain. Domain boundaries are aperiodically inserted, in contrast to the usual CS structures, forming an incommensurate structure.