Improved flux pinning behavior in bulk YBCO achieved by nano-alumina addition

Nanoparticles (∼10 nm) with a narrow size distribution have been embedded within the YBCO matrix of bulk superconductor in order to serve as effective flux pinning sites. In this study, alumina nano-pinning centres (∼10 nm) have been successfully introduced into YBCO superconducting matrix. The doping of alumina was realized by adding Al2O3 nanoparticles with a narrow particle size distribution to presintered bulk YBCO. The critical current density of these alumina-doped samples is significantly increased and the Jc-B behaviour is remarkably improved. Our results suggest that Al2O3-induced nano-pinning centres may have high pinning efficiency at a temperature around 77 K and be one of the main factors to improve the performance of YBCO. Our study reveals that nano-pinning centres are also a feasible solution to solve the pinning degradation at high temperature in YBCO