Influences of oxygen partial pressure on the phase composition of the (Bi, Pb)-2212 precursor powder

Abstract

Bi-2223 tapes, synthesized through the two-powder method, exhibit distinctive features such as high current density and a controllable secondary phase. Traditionally, the two-powder method involves the separate preparation of Bi-2212 and CaCuO powders followed by their mixing. However, during this process, it is necessary to dope the Bi-2212 powder with an appropriate Pb content to achieve a stable lattice structure in the Bi-2223 phase. The alteration of ion valences between Pb²⁺ and Pb⁴⁺ influences the oxygen content, thereby affecting the phase formation of (Bi, Pb)-2212 and, consequently, the final properties of Bi-2223 tapes. Surprisingly, limited research has explored the impact of the heat treatment process on (Bi, Pb)-2212. Consequently, this study investigates the phase composition and microstructure of (Bi, Pb)-2212 under various oxygen partial pressures to deepen our understanding of the effect of Pb on the composition of (Bi, Pb)-2212. Simultaneously, the behavior of Pb in the lattice of Bi-2212 is analyzed. Ultimately, the findings reveal that low oxygen conditions are advantageous for fabricating (Bi, Pb)-2212 powder with a high main phase content and a reduced secondary phase, thereby demonstrating excellent current-carrying performance in Bi-2223 tapes.