Effect of pre-annealing temperature and atmosphere on the microstructure and transport property of Bi-2223/Ag tapes

The phase assemblage and Bi-2212 texture in Bi-2223/Ag tapes before the heat treatment were varied by pre-annealing the tapes at different temperatures and in pure Ar or air for 10 h. Then all the tapes were isothermally heat treated at 840/spl deg/C in air for 4 cycles with intermediate pressings. The J/sub c/ of the samples pre-annealed in pure Ar were lowered no matter which annealing temperature was used. The best J/sub c/ was obtained in the samples pre-annealed at 800/spl deg/C in air, which was in an average value of 21.7 kA cm/sup -2/, being increased by 25% compared with that of the unannealed tapes (17.3 kA cm/sup -2/). The transport properties of various pre-annealed samples were correlated to the phase evolutions, growth and pre-alignment of Bi-2212 grains during pre-annealing.