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Effect of Li addition on the properties of Bi-based superconductors

2003-06-01
Ogun, SE
Ozkan, H
Hasanlı, Nızamı
The effect of Li addition on the formation and properties of Pb containing Bi-based superconductors has been studied. Three successive thermal sintering cycles have been applied to the oxides adjusted for the nominal composition, Bi1.6Pb0.4Sr2CaCu2O8+d. Eight different samples having Li2CO3 from 0.0 up to 3.0 weight% have been synthesized, X-ray diffraction patterns, resistivity-temperature behaviors and differential thermal analysis of the samples have been examined. Li2CO3 addition at 650degreesC decreases the fraction of (Bi,Pb)-2212 and increases that of Ca2PbO4. The normal state resistances of the samples increase, the onset T. values decrease and the lattice parameters almost,remain same with Li2CO3 addition. Li2CO3 addition up to 3.0 wt% decreases the melting temperature of (Bi,Pb)-2212 phase by about 50degreesC inducing a liquid phase at about 750degreesC. Our observations suggest that the high T-c phase, (Bi,Pb)-2223 may be formed at about 750-800degreesC using the precursors, (Bi,Pb)-2212 and Ca2PbO4 doped with Li2CO3.