High critical current density in RE–Ba–Cu–O bulk superconductors with very fine RE 2BaCuO 5 particles

Abstract

We have studied the microstructure and critical current density ( J c) of Gd–Ba–Cu–O and Y–Ba–Cu–O bulk superconductors. The size of RE 2BaCuO 5 (RE211) particles trapped in REBa 2Cu 3O y (RE123) matrix could be refined by employing ultra-fine RE211 powder as a precursor, which led to high J c values exceeding 1 × 10 5 A/cm 2 at 77 K in self-field for Gd–Ba–Cu–O. In the case of Y–Ba–Cu–O, however, the size reduction of Y211 led to inhomogeneous distribution of Y211 particles, in that the volume fraction of Y211 phase largely decreased near a seed crystal. We also studied superconducting properties of (Gd,Y)–Ba–Cu–O bulk material fabricated from precursor of Gd123-Y211. The employment of finely-milled Y211 powders resulted in a dramatic enhancement of J c values in this system. The maximum J c value for (Gd,Y)–Ba–Cu–O reached 2.5 × 10 5 A/cm 2 at 77 K.