Effect of (Pb,Bi)3Sr2Ca2CuOy phase on critical current density of Ag/(Bi,Pb)2Sr2Ca2Cu3O10 tapes

The effect of (Pb,Bi)(3)Sr2C2CuOy (3221) phase formation during post-annealing has been investigated. It was found that contents of the 3221 phase increased with annealing time when fully reacted (Bi,Pb)(2)Sr2Ca2Cu3O10 (2223) tapes were post-anneated at 780 degrees C up to 10 h, while the contents of the (Bi,Pb)(2)Sr2Ca2Cu3O10 (2212) phase remained almost constant. The critical current density and irreversibility field of the annealed tapes decreased monotonously with the increasing content in 3221 phase. Square-shaped 3221 particles were observed in both grains and grain boundaries situated on the ab-plane which are responsible for degradation of the critical current density and irreversibility field of the annealed tapes. The critical current density versus magnetic field showed an enhancement of weak link behaviour induced by 3221 phase for the annealed tapes which reduces the number of the strongly coupled grain boundaries. (C) 1998 Elsevier Science B.V.