Comparison of the Pinning Behavior of Nb3Al Superconductors Prepared by MAT and RHQT Methods

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 T-c, J(c), H-irr, and F-p, 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* approximate to 0.2; however, it is interesting to find that scaling exponents p and q appear to vary with sample's performance: when F-p,F-max > 1 GN/m(3), the characteristics of the p-F-p,F-max and q-F-p,F-max curves are different from those at F-p,F-max < 1 GN/m(3). Furthermore, H-irr-F-p,F-max curve also changes its character at F-p,F-max approximate to 1 GN/m(3). 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.

Automated summary

This paper investigates the pinning behavior of high-performance Nb3Al samples and finds that the scaling behavior of pinning force is dominated by the planar pinning mechanism. The variation of scaling exponents p and q with sample's performance suggests that the main source of planar pinning centers in high-performance Nb3Al may not be grain boundaries, but other planar defects.