Effect of vanadium and barium on the Bi-based (2223) superconductors

Two series of the superconducting materials with nominal composition Bi1.6−yVyPb0.4Sr2Ca2Cu3Oδ and Bi1.6−yVyPb0.4Sr1.6Ba0.4Ca2Cu3Oδ (where y = 0.0, 0.1, 0.2, 0.3) were prepared by the conventional solid-state reaction method. The effect of vanadium and barium substitution at Bi and Sr sites respectively, have been investigated by the X-ray diffraction, scanning electron microscopy, dc electrical resistivity, ac susceptibility and critical current density. Room temperature X-ray diffraction studies show that there exists two phases i.e. Bi-(2223) and Bi-(2212) in the analyzed samples. The evaluated crystalline lattice structure of the prepared sample mainly belongs to the superconductive orthorhombic Bi-(2223) and Bi-(2212) phases. The dc electrical resistivity data agree with the ac susceptibility measurements. The onset temperature Tc (onset) and zero resistivity critical temperature Tc (R = 0) of all the samples remains within the temperature range ≈112-116 ± 1 K and 104-108 ± 1 K respectively. The measurements showed that the highest Tc (R = 0) value of the superconducting sample is 108 ± 1 K, with composition Bi1.6Pb0.4Sr1.6Ba0.4Ca2Cu3Oδ. By increasing the vanadium concentration, an increase in the critical current density in both the series has been observed.