We have investigated the effects of Gd2BaCuO5 (Gd21l) addition on the microstructure and Jc-B properties of oxygen-controlled-melt-growth (OCMG)-processed (Nd, Eu, Gd)-Ba-Cu-O system with scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and magnetization measurements. Compositional analyses revealed that small RE2BaCuO5 (RE211; RE: rare earth elements) particles consist mainly of Gd in the RE site, while large RE211 particles contain Nd, Eu and Gd despite the fact that only Gd211 was added to the system. Both zero field and peak Jc increased with increasing Gd211 content; however, Jc values were decreased when the amount of Gd211 reached 40 mol%. The sample (Nd, Eu, Gd)Ba2Cu3Oy added with 30 mol% of second phase Gd211 showed respective critical current densities of 71 000 and 52 000 A/cm2 in O T and 2.6 T at 77 K for fields parallel to the c-axis. These results indicate that Gd211 addition to (Nd, Eu, Gd)-Ba-Cu-O is effective in improving Jc values through fine dispersion of Gd211.
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