Optimization of Partial Melting Process for Bi-2212 Multi-Filament Wires

Abstract Bi-2212 precursor powder was synthesized by a co-precipitation process, and 19×(36+1) multi-filament wires were prepared by traditional powder in tube (PIT) process. Both the maximum melting temperature, T max and cooling rate, R c1 have been optimized during partial melting process (PMP). The texture structures of Bi-2212 grains and secondary phase distributions were observed with the scanning electron microscopy. Differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA) were used to evaluate the thermodynamic properties of Bi-2212 wires. The phase transition process during cooling was discussed based on the analysis of both microstructure evolution and the thermodynamic investigation. It can be concluded that both T max and R c1 have great influences on the distribution of pores and secondary phase, such as alkali earth cuprate (AEC). The optimized critical current density of ∼4400 A·cm −2 at 77 K and self field can be obtained with the T max of 892 °C and a two-step cooling process at the R c1 of 40 °C/h.