Enhanced flux pinning and critical currents of YBa2Cu3O7-x films with self-assembled SrO2 nanoparticles generated by Eu0.6Sr0.4BiO3 buffer layers

YBa2Cu3O7− x (YBCO) is treated as a high-temperature superconductor material for its excellent performance. In this article, we investigated the superconducting properties of YBCO grown on LaAlO3 (LAO) substrate with Eu0.6Sr0.4BiO3 (ESBO) buffer layers. Though the chemical solution-based method, we get ESBO buffer with tetragonal SrO2 particles precipitated on the surface. The cross section of transmission electron microscopy shows more microstructure details of defects of YBCO films introduced by buffer layers and self-assembled SrO2. It is observed that the critical current density Jc of YBCO grown with buffer layers enhanced approximately 40% compared with those on LAO at a low applied magnetic field. The comparison of fitted curves of YBCO/ESBO with different pinning types shows that it is closer to δl pinning and began to lean to δ stress pinning with temperature arise. The values of pinning forces also get improved. Besides, the analysis of normalized pinning force density at 77 K demonstrates the interplay of different flux pinning mechanisms. Finally, all the results show the effectiveness of ESBO buffer layers on enhancing the performance of YBCO.