Boosting critical current density in Bi-2212/Ag round wires by precise tuning 14:24AEC phase

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Bi2Sr2CaCu2O x (Bi-2212)/Ag round wires prepared by the powder-in-tube method is a promising high-temperature superconductor for ultra-high field applications. The current capacity of Bi-2212/Ag wires is negatively affected by the impurity phase of Bi2Sr2CuO x (Bi-2201). In this work, a novel precursor powder fabrication technique was developed to eliminate the presence of large residual Bi-2201 grains and to enhance the critical current density (J c) of Bi-2212/Ag wires. Bi-2212 incorporating (Sr, Ca)14Cu24O y (14:24AEC) precursor powders was prepared using a combination of ultrasonic spray pyrolysis and calcination processes. The influence of the 14:24AEC phase on the phase, microstructure, melting behavior and superconducting properties of Bi-2212/Ag wires was systematically investigated. During the overpressure heat treatment, the addition of 14:24AEC into the wire promoted melting, effectively reducing the formation of large Bi-2201 grains. Moreover, the formation of narrow Bi-2201/Bi-2212 intergrowth and stacking faults were introduced into the Bi-2212 matrix. The Bi-2212/Ag wire with added 2 wt% 14:24AEC exhibited a maximum J c of 4670 A mm−2 at 4.2 K and 12 T. Therefore, precise tuning of the alkaline earth cuprate composition in precursor powders could be a valid approach for improving the current capacity of Bi-2212/Ag multi-filamentary wires.