(Nd, Eu, Gd)-Ba-Cu-O superconductors with combined addition of CeO₂ and Pt

A combination of CeO₂ and Pt doping has been performed for oxygen-controlled melt-growth processed (Nd, Eu, Gd)-Ba-Cu-O with the aim of refining the (Nd, Eu, Gd)₂BaCuO₅ particles, which were added to the (Nd, Eu, Gd)Ba₂Cu₃O_y (NEG-123) precursor. Observations using transmission electron microscopy demonstrate that sub-micrometre-sized 211 particles could be embedded successfully in the NEG-123 matrix. Energy dispersive x-ray analysis (EDX) confirmed that these sub-micrometre-sized 211 particles consisted mainly of Eu on the rare earth site for the samples containing 10 mol% (Nd, Eu, Gd)₂BaCuO₅. As a result, the (Nd, Eu, Gd)-Ba-Cu-O sample with a combined addition of CeO₂ and Pt exhibits an enhanced fishtail effect with a critical current density, J_c, of 73000 A cm^-2 at 3 T for fields parallel to the c-axis at 77 K.