Effect of High-Pressure Pre-Densification on Precursor Powder and Performance of Bi-2212 Wires

To address the issue of non-equilibrium phase transformation occurring in the precursor powder of Bi-2212 wires during the high-pressure pre-densification process, Multifilamental Bi-2212 wires were fabricated using a powder-in-tube method. The effect of high-pressure pre-densification (OP-PD) on the precursor powder phase composition and current-carrying capacity of the Bi-2212 wires was investigated. Results show that under OP-PD conditions at a total environmental pressure of 5.0 MPa, the wire diameter decreased by approximately 3%. With increasing oxygen partial pressure, significant partial decomposition of the Bi-2212 precursor powder occurred, forming Cu-rich and Bi-rich regions. After complete heat treatment (OP-HT), the high-pressure pre-densified wire filaments exhibited higher density and less residual secondary phase. Compared with wires directly subjected to OP-HT heat treatment from the as-processed state, their superconducting current-carrying capacity improved by more than 20%.