Microstructural characterization of the 85 K superconducting phase in the Bi−Ca−Sr−Cu−O system

Summary Transmission electron microscopy has been applied to investigate the microscopic features of a superconducting phase present in the system Bi−Sr−Ca−Cu−O. Sintered samples showing a single transition temperature of 85K, which points out the formation of aB-phase, were mechanically and ion-beam thinned. Electron diffraction shows that the Bi₂Sr₂CaCu₂O₈ superconductor possesses a primitive orthorhombic unit cell withPnnn space group. High-resolution electron microscopy reveals that the most common defect corresponds to a (001) lamellar structure caused from frequent twins with (001) composition plane and [001] fourfold axis twin operator. Possible derivative structures, essentially based on the occurrence ofm b/5+n a shifts everyc period, are discussed. To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.