A structural transformation and its effect on the physical properties of the V-substituted Bi2Sr2Ca2Cu3O10+y system

Systematic substitution of V in the Bi2-δVδSr2Ca2Cu3O10+y system (δ=0, 0.2, 0.4, 0.6, 0.8 and 1) was carried out in order to determine the effect of V ions on the phase formation and on the physical properties of the BSCCO 2223 system. The most interesting observation was structural transformation of the system from tetragonal to orthorhombic after δ=0.6. A solid solubility limit for V was also found to exist. Resistivity and susceptibility studies have shown that high-Tc superconductivity exists up to δ=0.6 and that the semiconducting-to-metallic transition or fully semiconducting behaviour occurs after this limit. A fractionally small but very-high-Tc transition at around 210 K was also observed, but it was not reproducible. Among the V-substituted samples the best electrical properties were obtained for δ=0.2; Tc and To were found to be 112 K and 92 K, respectively, the calculated value of Jc was found to be 1.11x105 A cm2 at 4.5 K and the thermal conductivity parameter κ was found to be 6.4 mW cm-1 K-1. By substituting the higher-valence state V5+ ions for Bi3+, the thermal treatment time is significantly reduced. The magnetic properties, IR and thermal conductivity results showed evidence of a strong coupling mechanism in the Bi2-δVδSr2Ca2Cu3O10+y system. (author)