Structure and composition of the 115 K superconducting phase in the Bi-Ca-Sr-Cu-O system

Abstract
Results of convergent beam electron diffraction and energy dispersive x‐ray (EDX) microanalysis of Bi1.2Ca0.9Sr0.9Cu2Oy superconductor are reported. The structure is orthorhombic with a=5.63 Å, b=5.4 Å, and c=38.2 Å. The c parameter is different from those reported by other workers and suggests that two extra perovskite units ap, where ap=3.82 Å, have been introduced leading to c=10ap. EDX microanalysis shows that the Cu content of this phase is higher than that reported by other workers. It is suggested that the phase with c=38.2 Å may be the higher temperature (115 K) superconductor.