Incommensurate crystallographic shear structure of Ba x Bi2 − 2x Ti4 − x O11 − 4x (x = 0.275)

Abstract

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-Bi2Ti4O11 and domain boundaries composed of TiO6 octahedra. Ba and Bi ions are accommodated in the cavities between TiO6 octahedra in the domain. Domain boundaries are aperiodically inserted, in contrast to the usual CS structures, forming an incommensurate structure.