STRUCTURE AND SUPERCONDUCTIVITY IN THE SINGLE CU-O LAYERED (BI2-XPBX)(SR2-YLAY)CUO6+DELTA-SYSTEM

The structural and superconducting properties of the series, Bi2-xPbxSr2-yLayCuO6+delta (x = 0.5, 0 less-than-or-equal-to y less-than-or-equal-to 1.0 and 0 less-than-or-equal-to x less-than-or-equal-to 1.0, y = 0.4), are studied. X-ray diffraction experiments show both series form a solid solution with a non-modulated orthorhombic structure over a wide range. Resistivity data shows metallic behavior and superconductivity with a maximum of T(c) = 29.5 K at x = 0.6, y = 0.4. The appearance of superconductivity correlates well with an oxygen content of 6 as measured by iodometric titration. A semiconducting-metallic-semiconducting transition was observed and kinks exist in both T(c) versus x (or y) and rho/rho-290 versus x (or y) curves. The fact that simultaneous substitution of Pb and La for Bi and Sr is necessary to stabilize the 30 K superconducting phase may indicate the importance of preventing structural disorder arising from Bi substitution onto the Sr site.