Improvement of reproducibility of high transport Jc for Bi2Sr2CaCu2Oy/Ag tapes by controlling Bi content

A new method to obtain high Jc Bi-2212/Ag tapes with high reproducibility was developed. Melt-solidifying with Bi2Al4O9 is found to be an effective method for suppressing the vaporization of bismuth oxide during the high-temperature heat treatment. By application of this method, the homogeneity of the microstructure of the Bi-2212 layer was improved considerably due to a decrease of the Bi-poor phase, (Sr, Ca)-Cu-O. The reproducibility of Jc values was also improved corresponding to the microstructure, and Jc maintained more than 1×105 A/cm2 at 4.2 K in 7 T even for a 1 m tape.