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

Abstract

YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7-</sub> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> (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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (LAO) substrate with Eu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.6</sub> Sr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.4</sub> BiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (ESBO) buffer layers. Though the chemical solution-based method, we get ESBO buffer with tetragonal SrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> 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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . It is observed that the critical current density J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> 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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">stress</sub> 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.