CHARACTERIZATION OF THE (BI2-XSBX)SR2CACU2OY SYSTEM

Samples of nominal composition (Bi2-xSbx)Sr2CaCu2Oy (0.1 less than or equal to x less than or equal to 0.3) are investigated. X-ray diffract ion and electron diffraction show that the (Bi2-xSbx)Sr2CaCu2Oy system has a monoclinic phase with the lattice parameters a=21.73 Angstrom, b=5.76 Angstrom, c=19.32 Angstrom and beta=95.0 degrees, except for th e tetragonal Bi-2212 phase. The results of energy dispersive X-ray spe ctroscopy reveal that Sb does not substitute for Bi in the Bi-2212 mai n structure, but forms the monoclinic phase of Bi4Sr4Ca2SbOy. The supe rconducting transition temperature, which is examined by electric resi stance and AC magnetic susceptibility, is constant at about 87 K. The reason why Sb cannot substitute for Bi in Bi2O2 layers has been discus sed from the point of view of coordination.