Identification of Y₂BaCuO₅ inclusions with flux pinning in powder melting-processed YBa₂Cu₃O_y

YBCO samples with different amount of Y₂BaCuO₅ (211) inclusions are prepared by a powder melting process (PMP). The 211 particles with average size less than 1 μm are dispersively distributed in the 123 matrix. The samples are re-annealed at 880 °C to eliminate the stacking faults and dislocations which commonly exist in the melt-processed samples. After this re-heat treatment the main extrinsic defects are 211 particles. The dc transport critical currents are measured on the samples at 77 K in magnetic fields up to 20 T. Magnetoresistance measurements are performed in fields up to 7.8 T. The results indicate that the 211 inclusions considerably influence the flux pinning behaviour of the melt-processed YBCO materials in magnetic fields up to 20 T.