X-Ray Structure Study of the High-T_c Phase of the Bi(Pb)–Sr–Ca–Cu–O System

Bulk samples of the (Bi,Pb)–Sr–Ca–Cu–O system were prepared by solid state reaction. The superconducting characteristics of samples with dominant 2223 phase were examined as a function of nominal lead concentration as well as their preparation. It is shown that for samples quenched in liquid nitrogen the superconducting transition temperatures T_c registered are lower than those for slowly cooled samples. This effect cannot be ascribed to concentration variations. X-ray diffraction (XRD) data are analysed using the Rietveld technique. The structure refinements enable to investigate small structure changes that can be related to variations of the lead substitution in Bi–O planes.