Nb and Ta substituted Bi(Pb)-Sr-Ca-Cu-O superconductors

The influence of stoichiometric replacement of Bi by Nb and Ta in the Bi(Pb)-based superconducting system has been investigated. The properties were detected by the measurement of resistivity, magnetic susceptibility and critical current density. X-ray diffraction technique has been used for crystallographic and phase analysis. The study reveals that for both substituents an addition of small amount of them enhances the content of the high temperature phase and improves superconducting properties. On the other hand greater amount of substituents deteriorates weak links in the sample.