Effect of the annealing time on the Pb concentration and phase composition of samples from the Bi-Pb-Sr-Ca-Cu-O system

The superconducting material with a nominal composition Bi 1.6 Pb 0.4 Sr 2 Ca 2 Cu 3 O y has been synthesised. The annealing time varied from 18 to 168 h for the different tests. It is established that the increase of annealing time leads to a reduction in Pb content and an increase in the volume of the 110 K 2223 phase, in relation to the 85 K 2212 phase. The results of the investigation indicate that the introduction of Pb in the crystal lattice hardly contributes to the increase in 2223 phase. A more probable explanation is that Pb causes the formation of a medium that helps the transformation of the 2212 phase into the 2223 phase.