VANADIUM SUBSTITUTED BI-PB-SR-CU-O SUPERCONDUCTORS

The effect of stoichiometric replacement of Pb and Bi by vanadium in t he Bi-based systems has been studied. In a series of samples with nomi nal composition BiaPbbVcSr4Ca5CU7Ox (a + b + c = 4) the influence of t he dopant was detected by measurement of the electrical resistivity, c ritical current density and magnetic susceptibility, by x-ray analysis and by SEM with an x-ray electron microprobe. The sample with substit ution of V for Bi and with content of Pb, b = 0.8, showed the highest content of the 2223 phase and improved intergrain boundaries. An incre asing substitution of V for Pb got worse superconducting properties. I n the samples with the composition Bi2.6Pb0.8V0.6Sr4Ca5Cu7Ox sintered for different time periods, vanadium was found in the form of various double oxides, mainly as Sr3V2O8 A certain amount of vanadium was dete cted in the 2223 phase by the Electron Microprobe, but it probably was some finely dispersed phase with a grain size below the resolution of our SEM. (C) 1997 academic Press Limited.