New method for introducing nanometer flux pinning centers into single domain YBCO bulk superconductors

• Single domain YBCO bulks with Bi2O3 additions fabricated by TSIG process.
• Nanoscale Y2Ba4CuBiOx(YBi2411) particles introduced by Bi2O3 additions.
• The YBi2411 particles are about 150 nm, can act as effective flux pinning centers.
• The optimal addition of Bi2O3 is 0.7wt% to achieve higher levitation force.
• The result is helpful to improve the quality of REBCO bulk superconductors.

Single domain YBCO superconductors with different additions of Bi2O3 have been fabricated by top seeded infiltration and growth process (TSIG). The effect of Bi2O3 additions on the growth morphology, microstructure and levitation force of the YBCO bulk superconductor has been investigated. The results indicate that single domain YBCO superconductors can be fabricated with the additions of Bi2O3 less than 2 wt%; Bi2O3 can be reacted with Y2BaCuO5 and liquid phase and finally form Y2Ba4CuBiOx(YBi2411) nanoscale particles; the size of the YBi2411 particles is about 100 nm, which can act as effective flux pinning centers. It is also found that the levitation force of single domain YBCO bulks is increasing from 13 N to 34 N and decreasing to 11 N with the increasing of Bi2O3 addition from 0.1 wt% to 0.7 wt% and 2 wt%. This result is helpful for us to improve the physical properties of REBCO bulk superconductors.