Heat treatment on phase evolution of Bi-2223 precursor powder prepared by spray pyrolysis method

The phase evolution of Bi-2223 precursor powder prepared by spray pyrolysis method is studied with different heat treatment parameters. The results show that the reaction temperature and phase composition of precursor powder depend on heat treatment atmosphere. Phase assemblage of (Bi,Pb)-2212, AEC, CuO, and small Bi-2201 can be obtained by heat-treated in N₂-0.1%O₂ atmosphere. For precursor powder, there is sufficient reaction process at 770 °C, and the dimension of Bi-2212 phase increases rapidly with the increase of heat treatment temperature and time. The dimension of AEC phase also increases by extending heat treatment time. As a balance among phase assemblage, dimension of particle and adequate reaction, a reasonable precursor powder can be obtained by heat-treated at 770 °C for 12 h-16 h in N₂-0.1%O₂ atmosphere. Critical current of 37-filament Bi-2223 tape is about 120 A, which confirms that these heat treatment parameters are reasonable.