The kinetic relationships and activation energy of Bi-based superconducting phase formation

Abstract In this paper, the kinetic relationships with regard to the informations of 2212 and 2223 superconducting phases have been studied for a Bi-based superconductor with 2223 nominal composition. The formation of the Pb-doped 2223 phase and the 2212 phase with or without Pb obey the nucleation and crystal growing model, whose kinetic equations are Q i =1− exp (− K i t n ), whereas the formation of 2223 phase in the Pb-free system belongs to the nucleus boundary shrinking model, and the equation is 1−(1−Q 2223 ) 1 3 =K 2223 t . It is proved that the factor controlling phase formation is the activation energy of the overall reaction. The optimum sintering temperature range for the formation and the transformation relationships between the high-temperature phase and low-temperature phase are discussed.