SYNTHESIS AND REACTION-MECHANISM OF THE HIGH-T-C-2223 PHASE IN THE (BI,PB)-SR-CA-CU-O SYSTEM

The synthesis and reaction mechanisms of the (Bi,Pb)(2)Sr2Ca2Cu3O10+de lta superconducting compound have been investigated. Based on density curves evolution, on simulation of different kinetic models, and on SE M observations confirming directly some proposed hypotheses, the forma tion mechanisms are explored and discussed in this paper. It was found that the conversion process of Bi-2212 to the Bi-2223 phase was compe titive, consisting of a one-dimensional diffusion-controlled nucleatio n-growth reaction with edge dislocation at early sintering stages and a two-dimensional heterogeneous growth at grain interfaces with prolon ged sintering. It was suggested that the origin of the liquid phase ac counting for the fast transformation of 2212 to 2223 comes from the re action between Ca2PbO4 and PbO. A reproducible processing protocol to develop the synthesis of the 110 K high-T-c phase in the solid-state r egime in large quantities is also presented, as is needed for applicat ions.