Abstract
Although grain boundary pinning as the main source has been clarified in A15-structured superconductors, the pinning properties in high-performance Nb3Al are still poorly understood. In this paper, a comparative study of the pinning behavior of some typical Nb3Al samples prepared by MAT and RHQT methods, which have different superconducting properties in Tc, Jc, Hirr, and Fp, is investigated. It is observed that the scaling behavior of the pinning force of these samples is dominated by the planar pinning mechanism, characterized by h*≈ 0.2; however, it is interesting to find that scaling exponents p and q appear to vary with sample’s performance: when Fp,max > 1 GN/m3, the characteristics of the p-Fp,max and q-Fp,max curves are different from those at Fp,max < 1 GN/m3. Furthermore, Hirr-Fp,max curve also changes its character at Fp,max≈ 1 GN/m3. This correlation between pinning force scaling behavior and performance supports the view point that the main source of planar pinning centers in high-performance Nb3Al may not be grain boundaries, but other planar defects such as stacking faults.