New-route of flux pinning enhancement in Nb3Al superconductor: density and orientation regulation of stacking faults by nano-oxide particles

Abstract The mechanism of critical current density (Jc) enhancement in rapid heating, quenching and transformation (RHQT) Nb3Al wires with nanoparticles was investigated from microscopic defects. As shown in transmission electron microscopy (TEM) results, stacking faults (SF) density in RHQT Nb3Al could be improved by incorporating nano-oxide particles, because the nanoparticles distorted the Nb3Al crystal lattice and the expansion of the distortion generated stacking faults. The macroscopic measurements based on electron backscatter diffraction (EBSD) showed that many stacking faults were parallel to the Lorentz force (FL//SF) in the pure sample, but orientation of stacking faults distributed randomly in the Nb3Al wires with nano oxide. Stacking faults that were normal to the Lorentz force (FL⊥SF) could hinder the motion of flux lines effectively and thus enhance the total flux pinning force (Fp). As a result, Jc of incorporated nano oxide Nb3Al wires were significantly elevated, where 1 at.% nano-ZrO2 and 1 at.% nano-Dy2O3 sample severally exhibited Jc values of 1.86×105 A/cm2 and 1.95×105 A/cm2@4.2 K,12 T, which improved by about 60% compared to the pure sample. The density and orientation regulation of stacking faults in RHQT Nb3Al revealed the new mechanism of Jc enhancement, which provided a new route to further improve the high-field Jc of Nb3A in future research.