We have investigated the effects of second phase (Nd, Eu, Gd)2BaCuO5 (NEG211) and platinum addition on the superconducting properties for (Nd, Eu, Gd)Ba2CUsOy (NEG123) composite prepared by the oxygen-controlled melt-growth (OCMG) process. The addition of NEG211 slightly decreased the critical temperature (Tc) and increased the critical current density (Jc), particularly in a low field region. The secondary peak effect, which is commonly observed in OCMG processed Nd123, was reduced with the NEG211 addition of >10%. Refinement of the NEG211 second phase was achieved by Pt addition, which led to a dramatic increase in both Jc values and the irreversibility field. Low field Jc varied as Vf/d, where Vfis the volume fraction and d is the mean diameter of NEG211, supporting the idea that the 211/123 matrix is responsible for the pinning-like melt-processed Y-Ba-Cu -O. However, in a high field region, due to the presence of additional pinning by field-induced pinning centers, such a relationship is not observed. Our results suggests that fine distribution of the second phase is effective in improving pinning properties in the (Nd, Eu, Gd)-Ba-Cu-O composite.
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