Effect of high-temperature vacuum degassing on microstructure and current-carrying capacity of the Bi-2212 wire

The voids in Bi2Sr2CaCu2Ox (Bi-2212) long-length wire should be eliminated as far as possible in order to improve its current-carrying capacity. There are several reasons for the void formation in Bi-2212 wire, mainly including the gas adsorbed on powder and existed in the gaps among the powder particles. We have found that the high-temperature vacuum degassing, which can eliminate the gases in wire and suppress the void formation, is an effective method to manufacture the Bi-2212 long wire with high-performance. Moreover, the high-temperature vacuum degassing is beneficial for the arrangement of Bi-2212 grains and the improvement of the texture of filaments. The engineering critical current density (Je) of Bi-2212 wire made by this method reaches to 440 A/mm2 at 4.2 K and 5 T. [Display omitted] •The impure gases are the main causes of the voids formation of Bi-2212 wire.•The vacuum degassing can eliminate the impure gases in the long Bi-2212 wire.•The Jc of the degassing wire is 2 times of that of the non-degassing wire.