A bismuth cobaltite with an intrinsically modulated misfit layer structure: [Bi0.87SrO2](2)[CoO2](1.82)

A new misfit layer cobaltite [Bi0.87SrO2](2)[CoO2](1.82) has been synthesiz ed. Its structure, solved from a single crystal X-ray investigation, shows CdI2 type [CoO2] layers similar to those encountered in misfit chalcogenide s, but different rock salt (RS)-type [Bi0.87SrO2] layers. In contrast to th e chalcogenides, these RS layers exhibit an intrinsic modulation due, as in the 2201 cobaltites, to the presence of double bismuth layers. Another fun damental difference with respect to misfit chalcogenides concerns the exist ence of strong Sr-O bonds between the [CoO2] layers and the [Bi0.87SrO2] la yers, instead of weak bonds. (C) 1999 Academie des sciences/Editions scient ifiques et medicales Elsevier SAS.