REBa2Cu3Oy superconductors with rare earth (RE) ions with large radii (RE: La, Nd, Sm) exhibit relatively low Tc due to the presence of RE-Ba solid solution. We have found that this solid solution can be suppressed if these superconductors are melt processed in a reduced oxygen atmosphere. We have also found that critical current densities of these superconductors are higher than those of melt processed YBa2Cu3Oy with fine Y2BaCuO5 inclusions in a high field region. The irreversibility line was also shifted toward the higher H-T region. We believe that flux pinning in these superconductors is ascribable to a finely distributed RE(Ba1–x, REx)2Cu3Oy phase in a good superconductive matrix.
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