Flux pinning by Gd-211 particles in ternary (Nd_0.33Sm_0.33Gd_0.33)Ba₂Cu₃ O_y melt-processed superconductors

Sub-micron Gd₂BaCuO₅ (Gd-211) particles were embedded in the ternary (Nd_0.33Sm_0.33Gd_0.33)Ba₂Cu₃ O_y (NSG-123) melt-textured superconductors. To enhance critical current density at low fields, different amounts of the secondary phase were added and refined by addition of 0.5 mol% Pt and 1 mol% CeO₂. Optical and scanning electron microscopy indicated sub-micron, mostly Gd-211, particles in the final product. Critical currents in remanent state increased monotonously with 211 concentration but the secondary peak did not nearly change. Critical current density of 100 kAcm^-2 at 77 K and the applied field of 2 T was achieved in the NSG-123 sample with 10 mol% Gd-211.