Modulation of superconducting grain structure to achieve high critical current in Ba0.6K0.4Fe2As2 multifilament round wires

Abstract

Iron-based superconducting wires fabricated by the powder-in-tube method are promising candidates for practical applications due to their prominent high-field performance. The morphology, compactness and alignment of the superconducting grains, which are mainly determined by the deformation and post-sintering strategy, have a large significance for the current carrying ability. Herein, we apply a stainless steel/AgSn/Ag composite architecture combined with a scalable groove rolling process to fabricate high-performance iron-based superconducting multifilamentary round wires. Highly dense superconducting filaments are obtained without hot-isostatic-pressing. A critical current density Jc= 3.02 × 104 A/cm2 at 4.2 K and 10 T is achieved, which is the highest value ever reported in iron-based multifilament wires. Through detailed microscopic and theoretical analysis, we conclude the deformation mechanism of Ba0.6K0.4Fe2As2 grains and discuss its influence on the supercurrent transport properties. We suggest that higher Jc can be achieved by introducing a better grain texture. Our method provides a simple and cost-effective way to densify practical superconducting wires and is very promising to be scaled up to long wire productions.