Synthesis and reaction mechanism of the high- Tc 2223 phase in the (Bi,Pb)SrCaCaCuO system

Abstract

The synthesis and reaction mechanisms of the (Bi,Pb) 2Sr 2Ca 2Cu 3O 10+δ superconducting compound have been investigated. Based on density curves evolution, on simulation of different kinetic models, and on SEM observations confirming directly some proposed hypotheses, the formation mechanisms are explored and discussed in this paper. It was found that the conversion process of Bi-2212 to the Bi-2223 phase was competitive, consisting of a one-dimensional diffusion-controlled nucleation-growth reaction with edge dislocation at early sintering stages and a two-dimensional heterogeneous growth at grain interfaces with prolonged sintering. It was suggested that the origin of the liquid phase accounting for the fast transformation of 2212 to 2223 comes from the reaction between Ca 2PbO 4 and PbO. A reproducible processing protocol to develop the synthesis of the 110 K high- T c phase in the solid-state regime in large quantitites is also presented, as is needed for applications.