Submicron size Gd₂BaCuO₅ particles as source for large critical current densities in (Nd_0.33Eu_0.33Gd_0.33)Ba₂Cu₃O_y

The effect of (Nd_0.33Eu_0.33Gd_0.33)₂BaCuO₅ (NEG-211), and Gd₂BaCuO₅ (Gd-211) additions on melt-processed (Nd_0.33Eu_0.33Gd_0.33)Ba₂Cu₃O_y (NEG-123) composites are investigated using a combination of transmission electron microscopy (TEM) and measurements of critical current densities, J_c. TEM observations demonstrate that we could successfully embed submicron-size 211 particles within the NEG-123 matrix. EDX analysis revealed that these submicron-size particles consist mainly of Gd in the rare earth site. The presence of such 211 particles leads to a dramatic increase of J_c in low fields as well as in the high field region. For NEG-123 with an addition of 40 mol% of NEG-211 a critical current density of 70 000 A/cm² at 77 K, 2.2 T is observed for the field applied parallel to the c axis.