Synthesis of Cuprates of Perovskite Structure in the Ba-Pb-Cu-O, Ba-Bi-Cu-O, and Ba-Pb-Tl-Cu-O Systems: Possible High Tc Superconductivity in a Perovskite-like Phase in the Ba-Pb-Tl-Cu-O System

Cubic cuprates (a ∼ 18.6 Å) with a BaCuO2-type structure were obtained in the Ba-Pb-Cu-O and Ba-Bi-Cu-O systems by the reaction of the component oxides at a high temperature (1370-1420 K), followed by quenching. By annealing these phases in oxygen at 1070-1120 K, perovskite-like phase (a ∼ 4.3 Å) of the formulae BaPb1-x Cu x O3-y and BaBi1-x Cu x O3-y (0 < x ≤ 0.5) were obtained. A perovskite of nominal composition BaPb0.25Tl0.25 Cu0.5O3-y , prepared by a similar procedure, was found to be superconducting with a T c of ∼ 70 K.