Groove-rolling as an alternative process to fabricate Bi-2212 wires for practical applications

Bi2Sr2CaCu2O8+x (Bi-2212) superconducting long-length wires are mainly limited in obtaining high critical current densities (J(C)) by the internal gas pressure generated during the heat treatment, which expands the wire diameter and dedensifies the superconducting filaments. Several ways have been developed to increase the density of the superconducting filaments and therefore decrease the bubble density; much higher critical currents have been reached, always acting on the final as-drawn wires. We here try to pursue the same goal of having a denser wire by acting on the deformation technique, through a partial use of groove-rolling at different wire processing stages. Such a technique has greater powder compaction power, is straightforwardly adaptable to long-length samples, and allows the fabrication of samples with round, square or rectangular shape depending on the application requirements. In this paper we demonstrate the ability of this technique to increase the density in Bi-2212 wires, which leads to a three-fold increase in J(C) with respect to drawn wires, making this approach very promising for fabricating Bi-2212 wires for high magnetic field magnets, i.e. above 25 T.