Optimization of the BaSnO₃ Doping Content in GdBa₂Cu₃O₇-δ Coated Conductors by Pulsed Laser Deposition

We tried to optimize the BaSnO₃ (BSO) doping content in GdBa₂Cu₃O_7-δ (GdBCO) coated conductors (CCs) on CeO₂-buffered ion-beam assisted deposition (IBAD)-MgO templates. The BSO-doped GdBCO CCs with various x vol% (x = 0, 2, 3, 4, 5, and 6) relative to GdBCO were prepared at 800 .C with the oxygen pressure of 300 mtorr by pulsed laser deposition (PLD), and their pinning properties were characterized by measuring magnetic hysteresis curves for the applied field parallel to the c-axis of GdBCO (B//c) up to 5 T and fieldorientation dependence of transport critical currents for 1, 3, and 5 T at 65 and 77 K, respectively. Among all samples, a 5 vol% BSO-doped GdBCO CC exhibited the highest maximum pinning force density (Fp,max) values of 32.5 GN/m3 near 4 T at 65 K and 6.5 GN/m₃ near 3.2 T at 77 K, for B//c (θ = 180.), and also the highest minimum transport critical current density (Jc,min) of 0.39 MA/cm2 at 77 K in 1 T and 0.68 MA/cm² at 65 K in 3 T, for θ = 120., evidencing that 5 vol% is the optimum BSO content. Observation of BSO-doped GdBCO CCs by transmission electron microscopy revealed that the effective flux pinning of BSO-doped GdBCO CC was attributed to the BSO nanorods of ∼-10-nm diameters roughly aligned along the c-axis of the GdBCO matrix.