Engineering nanocolumnar defect configurations for optimized vortex pinning in high temperature superconducting nanocomposite wires

We report microstructural design via control of BaZrO 3 (BZO) defect density in high temperature superconducting (HTS) wires based on epitaxial YBa 2 Cu 3 O 7-δ (YBCO) films to achieve the highest critical current density, J c , at different fields, H . We find the occurrence of J c ( H ) cross-over between the films with 1–4 vol% BZO, indicating that optimal BZO doping is strongly field-dependent. The matching fields, B φ , estimated by the number density of BZO nanocolumns are matched to the field ranges for which 1–4 vol% BZO-doped films exhibit the highest J c ( H ). With incorporation of BZO defects with the controlled density, we fabricate 4-μm-thick single layer, YBCO + BZO nanocomposite film having the critical current ( I c ) of ~1000 A cm −1 at 77 K, self-field and the record minimum I c , I c (min), of 455 A cm −1 at 65 K and 3 T for all field angles. This I c (min) is the largest value ever reported from HTS films fabricated on metallic templates.