An x-ray diffraction and electron microscopic study of a new high-T_csuperconductor based on the Bi-Ca-Sr-Cu-O system

Observed high-resolution images of a new high-T_csuperconductor based on the Bi-Ca-Sr-Cu-O system (T_cabove 70 K) indicated a structure derived from the Bi₄Ti₃O₁₂type in whichdoubled bismuth oxide layers alternate with double perovskite layers along the c-axis. The orthorhombic unit cell dimensions showed an approximate relation of a=√2a_pb=5√2a_pand c=8a_pwhere a_p=3.82 Å, the cell parameter of a cubic perovskite. At least a quarter of the oxygen should be deleted in accordance with the average copper valence of less than 3 and two-dimensional Cu-O layers are supposed to be responsible for the high-T_csuperconductivity.