Critical current density improvement of RHQT Nb3Al superconducting wires by incorporating magnetic Dy2O3 nanoparticles as additional flux pinning centers

In this paper, we prepared magnetic Dy2O3 nanoparticles (n-Dy2O3) doped Nb3Al superconducting wires by rapid heating, quenching and transformation (RHQT) method, and investigated the micro-defects, superconducting properties and flux pinning mechanisms. TEM results showed high-density stacking faults (SF) with spacing of 5-25 nm located in Nb3Al (210) crystal planes, which is due to the absence of Nb atoms on the {100} crystal planes. Additionally, many intra-granular and inter-granular Dy2O3 nanoparticles with size of 4-40 nm were also observed in the Nb3Al superconducting phase. Jc was promoted in the doped samples, obtaining the best Jc of 1.95 x 105 A/cm2@ 4.2 K, 12 T in 1 at.% n-Dy2O3 doped Nb3Al wire, which was nearly 70 % higher than pristine Nb3Al wire. By doping n-Dy2O3, the fP(Fp/Fp,max)-h(B/Birr) peaks shift to larger h value (higher field). The flux pinning mechanism by fitting fP-h curves showed dominant surface pinning combined with point pinning, corresponding to the crystal defect of stacking faults and nanoparticles, respectively. The pinning mechanism verified that the nanoparticles acted as additional pinning centers to significantly elevate the Jc performance.