Kinetics of phase formation and transport properties of Bi-2223/Ag tapes fabricated by various calcined powders

The kinetics of phase formation and transport properties of Bi-2223/Ag tapes fabricated by precursor powders with different phase assemblages have been studied. Our results show that the formation process of 2223 phase is strongly related to the secondary phases in precursors. A variation of the reaction-order, n, deduced from the Avrami relation, was observed along with the whole sintering processing. Within a sintering period of 65 h, n keeps the value of 0.7 for the tape made from the powder calcined at 830/spl deg/C, while it changes from 0.3 or 0.4 to 1 for the tapes prepared with the powders calcined at 810/spl deg/C and 820/spl deg/C. Based on the analysis of phase formation and transport properties, the optimum calcination conditions for achieving high J/sub c/ tapes are discussed.