Ag/YBCO superconducting round wires fabricated by bimaterial 3D printing

YBa2Cu3O7-δ (YBCO) superconductors have been widely applied in fields such as power electronics, due to their high critical temperature and excellent current-carrying capacity under high magnetic fields. However, long-length round wires, with the greatest potential for power transmission and large-scale magnets, still face challenges: due to the material’s intrinsic brittleness, difficulties in ensuring structural integrity and uniformity during sintering, and ineffective control over crystallographic texture within the round-wire geometry. Herein, we present a direct-ink-writing bimaterial 3D printing strategy to continuously fabricate submillimeter-diameter Ag/YBCO composite wires. Silver paste and ceramic slurry are used as precursors to form core-shell filaments. During the sintering process under an oxygen environment, Ag+ incorporates into YBCO lattice, which forms coherent interfaces with the superconducting phase and promotes [001] grain growth in round-wire. This texture forms intrinsically through solid solution, distinct from conventional seed-mediated or buffer-layer-assisted methods. Electrical transport measurements achieved a transport critical current density of 1.27×104 A·cm-2 @26 K, along with a high bending fracture energy of 1361.8 MJ·m-3. This work paves the way for scalable fabrication of long-length and high-performance superconducting round wires for magnets and compact power transmission cables.