Enhanced Flux Pinning and Critical Currents of YBa2Cu3O7−x Films With Self-Assembled SrO2 Nanoparticles Generated by Eu0.6Sr0.4BiO3 Buffer Layers

YBa
₂
Cu
₃
O
_7-
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 LaAlO
₃
(LAO) substrate with Eu
_0.6
Sr
_0.4
BiO
₃
(ESBO) buffer layers. Though the chemical solution-based method, we get ESBO buffer with tetragonal SrO
₂
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 SrO
₂
. It is observed that the critical current density J
_c
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.