Effect of lead addition to Bi-based 2222 superconducting cuprates Bi 2-xPb xSr 2(Y, Ce) 2Cu 2O 10+δ

Bi _2-xPb _xSr ₂(Y, Ce) ₂Cu ₂O _10+δ, a new family of lead containing Bi-2222 compounds has been synthesized and effects of annealing in high pressure of oxygen studied. Lead-free Bi ₂Sr ₂(Y, Ce) ₂Cu ₂O _10+δ synthesized under flowing oxygen is known to be non-superconducting, but annealing under high oxygen pressure (100 bar) at 500°C, induced superconductivity with T_c=25 K. On substitution of lead ( x>0.4), the superconductivity appears even in samples synthesized under flowing oxygen (1 bar). T_c increases with oxygen annealing pressure for all compositions, and it also increases with Pb content at a given oxygen pressure. These findings are discussed.