Critical current density and microstructure variations in YBa₂Cu₃O_7−x + BaSnO₃ films with different concentrations of BaSnO₃

Previous work on YBa₂Cu₃O_7−x (YBCO) + BaSnO₃ (BSO) films with a single composition showed significant critical current density (J_c) improvements at higher fields but lowered J_c in low fields. A detailed study on BSO concentrations provided here demonstrates that significant J_c enhancement can occur even up to 20 mol% BSO inclusion, where typical particulate inclusions in these concentrations degrade the YBCO performance. YBCO + BSO films were processed on (100) LaAlO₃ substrates using premixed targets of YBa₂Cu₃O_7-x (YBCO) with additions of 2, 4, 10, and 20 mol% BSO. The critical transition temperature T_c of the films remained high (>87 K), even with large amounts (20 mol%) of BSO. YBCO + BSO films showed a gradual increase in J_c at high fields as the amount of BSO was increased. More than an order of magnitude increase in J_c was measured in YBCO + BSO samples as compared to regular YBCO at 4 T. YBCO + 10 mol% BSO films showed overall improvement at all the field ranges while YBCO + 20 mol% BSO was better only at high fields. Transmission electron microscopy revealed the presence of ∼7–8-nm-diameter BSO nanocolumns, the density of which increased with increasing BSO content correlating well with the observed improvements in J_c.