magnetic and structural properties of bi(2223)doped by pb and sb

in a systematic approach, we have investigated the effect of the presence of pb and sb in the bi site in a bscco (2223 phase) superconductor. there are some contradictory reports in substitution of sb in the bi site. some researchers report an increase in the tc of these materials. so, we have made an accurate stoichiometry of these superconductors and selected extra pure starting materials with appropriate ratios of pb+sb.   the susceptility of these samples have been measured and the structures of the systems have been studied by sem and xrd. the results of this investigation show that, although the presence of pb is essential for formation of (2223) phase, but addition of small amount of sb helps to stabilize and enhance the ratio of higher phase. our results show that, presence of sb would raise the critical current density, but would not affect the tc of these superconductors.