Anionic substitutions in Bi-2223 superconductor Original Research Article

Samples of nominal stoichiometry Bi1.6Pb0.4Sr2Ca2.5Cu3.5Ox−zFz and Bi1.6Pb0.4Sr2Ca2.5Cu3.5Ox−z(SO4)z (z=0, 0.3, 0.6 and 0.9) were prepared by standard solid state reaction from appropriate oxides, carbonates, copper (II) fluoride, and copper (II) sulphate. Superconducting properties of the samples were characterized by measuring of temperature dependency of their electrical resistivity and critical current density, their phase composition was determined by X-ray diffraction (XRD) and element composition by X-ray fluorescence (XRF). While greater amount of fluorine widens the superconducting transition and worsens transport properties, the less doped sample shows increase in critical current density. Sulphur-doped samples show no superconducting transition at all.