We have investigated the superconducting properties of (Nd, Sm, Eu, Gd)-Ba-Cu-O composites prepared by the oxygen-controlled-melt-growth (OCMG) process. X-ray diffraction analyses confirmed that the main phase is REBa2Cu3Oy (RE is rare earth elements) with a small amount of the second phase RE2BaCuO5. Compositional analyses revealed that four RE elements were distributed uniformly with their ratio almost identical to the nominal composition. The samples showed relatively high Tc values of 93.5-95 K with a sharp superconducting transition. A clear secondary peak effect was observed in the magnetization curves. High resolution transmission electron microscopic observation, however revealed that unlike RE-Ba-Cu-O compounds, in which the RE site was compounded with two or three RE elements, clear strain fields were observed in the matrix, showing that the crystal defects were introduced by mixing four RE elements.
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