Characterization of the (Bi2−xSbx)Sr2CaCu2Oy system

Abstract Samples of nominal composition (Bi 2− x Sb x )Sr 2 CaCu 2 O y (0.1≤ x ≤0.3) are investigated. X-ray diffraction and electron diffraction show that the (Bi 2− x Sb x )Sr 2 CaCu 2 O y system has a monoclinic phase with the lattice parameters a =21.73A, b=5.76A, c=19.32Aandβ=95.0°, except for the tetragonal Bi-2212 phase. The results of energy dispersive X-ray spectroscopy reveal that Sb does not substitute for Bi in the Bi-2212 main structure, but forms the monoclinic phase of Bi 4 Sr 4 Ca 2 SbO y . The superconducting transition temperature, which is examined by electric resistance and AC magnet susceptibility, is constant at about 87 K. The reason why Sb cannot substitute for Bi in Bi 2 O 2 layers has been discussed from the point of view of coordination.