Effect of RE2BaCuO5 refinement on the critical current density and trapped field of melt-textured (Gd, Y)–Ba–Cu–O bulk superconductors

We have investigated the superconducting properties of (Gd, Y)–Ba–Cu–O bulk superconductors fabricated from precursors of the Gd123–Y211 with small additions of Pt and CeO2 in a reduced oxygen atmosphere. The employment of ball-milled ultra-fine Y211 powder as a precursor material was very effective in enhancing critical current density (Jc), since RE211 inclusions in the melt-textured samples could be drastically refined with decreasing the particle size of Y211 starting powder. The maximum Jc value reached an extremely high value of 380 kA/cm2 at 77 K in self-field. However, size reduction of RE211 led to inhomogeneous distribution of RE211 inclusions. The amount of RE211 was extremely small in the vicinity of a seed crystal, when the ultra-fine Y211 powder was employed. The trapped magnetic fields of Ag-added single-grain samples 25 and 33 mm in diameters were 1.5 and 2.0 T at 77 K, respectively.