HREM study of the fullerenoïd oxide Sr33Bi24+δAl48O141+3δ/2: Evidence of non-stoichiometry

A Transmission Electron Microscopy study of the complex bismuth strontium aluminate Sr33Bi24+δAl48O141+3δ/2, which exhibits an exceptional face centred cubic structure built up as a nest of spheres, is reported. One sphere exhibits an Al84 “fullerene” like configuration. Due to the complex distribution of the BiSrO atoms, which adopt an onion like sub-nanostructure, the correlation between the high resolution electron microscopy images and the different structural units has been established using the X-ray structural parameters refined from the single crystal study. The origin of point like variations of the contrast is discussed in terms of non-stoichiometry.