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

Two series of the superconducting materials with nominal composition Bi1.6-yVyPb0.4Sr2Ca2Cu3Odelta and Bi1.6-yVyPb0.4Sr1.6Ba0.4Ca2Cu3Odelta (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 Xray 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 T, (onset) and zero resistivity critical temperature T-c (R = 0) of all the samples remains within the temperature range approximate to 112-116 +/- 1 K and 104-108 +/- 1 K respectively. The measurements showed that the highest T-c (R = 0) value of the superconducting sample is 108 I K, with composition Bi1.6Pb0.4Sr1.6Ba0.4Ca2Cu3Odelta. By increasing the vanadium concentration, an increase in the critical current density in both the series has been observed. (c) 2005 Elsevier B.V. All rights reserved.