A series of superconductors with a nominal composition of Bi2CaSr2(1−x)Cu2O8−2x+δ or Bi2CaSr2 Cu2(1−y)O8−2y+δ, where 0≤x, y≤0.6, was prepared under identical conditions at 830°C. Their superconductivity degraded rapidly if x or y was larger than 0.4. from X-ray diffraction studies, it was suggested that vacancies were created when part of the SrO or CuO was removed from the Bi2CaSr2Cu2O8+δ. The extra oxygen stoichiometry, δ, decreased with increasing x but increased with increasing y. When δ was in between 0.04 and 0.18, Tc(zero) of Bi2CaSr2Cu2O8+δ was not dependent on δ and it was found to be about 60 K. Above this range, Tc(zero) decreased rapidly.
