Increase of Tc and disappearance of the structural modulation in the system Bi-Sr-Sm-Ce-Cu-O upon Pb substitution

The substitution of bismuth by lead was performed in the compound Bi2-xPbxSr2(Sm0.85Ce0.15)2Cu2O10+y. Its influence on the superconducting properties as well as on the structure was studied by X-ray diffraction, transmission electron microscopy (TEM) and various transport measurements. Lead was found to replace bismuth up to approximately x = 1, superconductivity occurring with a maximum Tc of 34-36 K at concentrations of x greater than 0.6. Resistivity data show a transition from semiconducting to metallic/superconducting behavior. Increasing lead content is accompanied by a decrease in the oxygen content with a corresponding decrease of the structural modulation which is directly correlated to the excess oxygen. At x = 0.9 this compound does not show a structural modulation, but still superconducts at 36 K. © 1990.