Flux pinning and superconducting properties of ZnO added (Nd,Eu,Gd)Ba₂Cu₃O_y

The paper provides an experimental basis for preparing large grain (Nd_0.33Eu_0.27Gd_0.39)Ba₂ Cu₃O_y "NEG-123". MgO seeds proved to be efficient in controlling growth orientation when a small quantity of ZnO of around 0.035 wt.% was added to the NEG-123 matrix. A substantial reduction of liquid phase loss was observed for a proper ZnO concentration. A perfect facet line up to the bottom of the sample with c-axis reflection plane was observed after the melt-growth implying high density of the material and practically no liquid loss. The magnetization measurements suggested that the superconducting transition temperatures were not affected up to 0.035 wt.% ZnO addition. Critical current density J_c, measured at 3 T and 77 K (H_a∥c-axis), increased with increasing ZnO content up to 0.035 wt.%, where it reached maximum value of 100 kA/cm² and decreased thereafter. The scalling analysis of the pinning force density as a function of the reduced field h = H_a/H_irr (H_irr is the irreversibility field) showed a peak at relatively high position as expected for an optimized pinning structure. The present results indicate high potential of ZnO particles for further enhancement of the material performance.