YBaCuO prepared by the Melt-Powder-Melt-Growth (MPMG) process has high critical current density over 30,000 A/cm2 at 77K and 1T. It has been found that non-superconducting Y2BaCuO5 (211) particles dispersed in the 123 superconducting phase are responsible for high J c values. The values of critical current densities increased with increasing the volume fraction of the 211 particles. An anomalous second peak was observed in magnetization loops for some samples which showed a broad T c transition in AC measurements, suggesting that some kinds of defects are responsible for the peak.
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