Top-seeded infiltration growth processing of single grain (Gd, Dy)BaCuO superconductors: Nano Nb₂O₅ doping, enhancement of trapped field and superconducting performance

Optimal doping of effective nano-inclusions improve the flux pinning ability of high-temperature superconductors. In continuation of optimization of single grain (Gd, Dy)Ba₂Cu₃O_7‒δ ((Gd, Dy)BCO/123) bulk growth conditions via top-seeded infiltration growth process, present work aims further improvement of the flux pinning abilities via addition of ~ 100 nm sized Nb₂O₅ particles (0 – 0.4 wt%). Structural analysis through Rietveld refinement and elemental analysis elucidated different phases evolved in view of Nb partial doping with Gd-Dy-Ba-Cu-O system. Microstructural analysis combined with the elemental analysis indicated the fine sized mixed (Gd, Dy)₂BaCuO₅ particles distribution with no Nb substitution. While, the substitution of Nb in the 123-matrix phase was increased with doping amount. The superconducting transition temperature determined magnetically, and electrical resistivity are ~ 93 K and ~ 94.3 K respectively, not affected seriously by the Nb₂O₅ doping due to slightly over doping of holes. The (Gd, Dy)BCO superconductor doped by 0.3 wt% of Nb₂O₅ was observed to be best relation which supported superior superconducting critical current density (increased more than 40%) up to high applied magnetic fields and trapped field performance at 77 K. Scaling of the flux pinning force indicated the presence of mixed pinning mechanisms originated in (Gd, Dy)BCO due to doping of Nb.