Thickness dependence of critical current density in YBa₂Cu ₃O_7-δ films with BaZrO₃ and Y ₂O₃ addition

We report the thickness dependence of critical current density (J _c) in YBa₂Cu₃O_7-δ (YBCO) films with 5mol% BaZrO₃ (BZO) and 5mol% Y₂O₃ additions grown on single crystal SrTiO₃ substrates by pulsed laser deposition (PLD). The results show that adding BZO+Y₂O₃ has reduced the thickness dependence of the self-field critical current density (J_c^sf), compared to that observed in optimized YBCO films, with a significant enhancement of J_c^sf in the thick film region (>2νm). The so-called 'dead layer' did not appear until the film thickness was greater than 6.4 νm. We attribute this improvement to the additional pinning centers introduced in the bulk by the addition and a decrease in microstructure degradation with thickness. As a result, J_c ^sf remains as high as 2.3MAcm^-2 in a 6.4 νmthick film. The combination of this high J_c^sf value and the enhancement of the in-field J_c induced by the additions, which was observed in the whole thickness range, leads to a critical current per centimeter width (I_c-w) in excess of 400Acm^-1 at 1T and 75.5K and 530Acm^-1 at 3T and 65K under all field directions.