Abstract
The Bi-Sr-Fe-O system has been revisited by transmission electron microscopy techniques. Three new layered oxides have been isolated and characterized. The first two oxides, Bi0.82Sr2 92FeO6-δ and Bi0.38Sr2.54Fe1.08O5-δ, exhibit a 2201- and a 1201-type structure respectively, related to superconducting cuprates. Both oxides are characterized by mixed layers with a 1/1 ordering between Bi and Sr species. The transition from 2201 structure to 1201 structure occurs through a complex intergrowth mechanism and leads to an intermediate structure, formulated as Bi1.21Sr5.12Fe2O11-δ. It corresponds to a regular stacking between the 1201 motif and the 2201 motif. These results are discussed in comparison with those previously obtained for the Bi-Sr-M-O systems (M ˭ Cu, Mn or Co).