Synthesis and phase relations of the 110 K superconducting 2223 phase in the Bi - Pb - Sr - Ca - Cu - O system

The influence of starting composition, especially the Bi:Pb ratio, on the formation of the 110 K superconducting 2223 phase was investigated. Compositional limits for `pure' 2223 have been preliminarily determined in terms of Pb versus Bi + Pb. In samples with nominal composition (d = 0), 2223 forms when . The 2223 phase coexists with 2212 in the range (i.e. with 10 - 20 mol% Bi replaced by Pb) after annealing at for 100 h. Some is also found. The 2223 phase was the only superconducting phase in samples where x > 0.4; was also found in these samples. `Pure' 2223 was obtained in samples with nominal composition when x = 0.4 and d = 0.1, 0.2, 0.3. The 2223 phase can be formed from starting compositions with less than 10 mol% Bi replaced by Pb, provided (Bi + Pb) > 2. The 2201 phase coexists with 2223 when (Bi + Pb) > 2.3 and Pb > 0.2.