The Effects Of Heat Treatments On Critical Current Density And Microstructure Of Bi-2223/Ag Tapes

The Bi-2223/Ag superconducting tapes were made by the two cold rolling / heat treatment cycles. The temperature of middle heat treatment was 835 degrees C for 30 to 100 hours. The temperature of final heat treatment was as same as that of previous heat treatment, but for 100 to 200 hours. Our results indicate that the middle heat treatment affects strongly on the Jc of tapes. The microstructure of Bi-2223/Ag tape with different Jc values has been studied by SEM. The chemical composition of each phase has been determined by EDX in the SEM. The SEM analysis reveals larger size of 2223 grains and better connection between 2223 grains in the best tape, and more inclusions and more defects in the tapes with lower Jc value. The relationships among the heat treatment conditions, the microstructure and the transport properties of the tapes have been discussed in this work.