Flux pinning by NiO-induced nano-pinning centres in melt-textured YBCO superconductor

Nano-pinning centres (similar to 10 nm) have been successfully introduced into melt-textured YBCO by doping NiO. The doping of NiO was realized by adding NiO nanoparticles to presintered YBCO followed by melt-texture processing. This method can reduce the substitution level of Ni in the YBCO matrix and can create Ni-rich second-phase precipitates with a size around 10 nm. The critical current density of these Ni-doped samples is significantly increased and the J(c)-H behaviour is remarkably improved. Our results suggest that NiO-induced nano-pinning centres may have high pinning efficiency at a temperature around 70 K and be one of the main factors for improving 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.