Superconductivity and structural change in the (Bi 2− yPb y)Sr 2 (Eu 2− xCe x)Cu 2O z system

Abstract

Superconductivity and crystal structure change have been observed in the Bi(Pb)-2222 system of (Bi 2− y Pb y )Sr 2 (Eu 2− x Ce x )Cu 2O z . By substitution of Pb for Bi, the samples easily become superconductors without annealing under high-pressure O 2 atmosphere. Then, when the Pb content y is increasing and exceeds 0.5, the crystal structure changes from a pseudotetragonal structure to an orthorhombic one. Interestingly, with increasing of the y value, the T c value monotonously increases, while the superconducting volume fraction shows a maximum at y=0.5.