Pinning mechanism of the high critical current density Sm-Ba-Cu-O superconductors with Sm210/Pd/Pt/CeO/sub 2/ addition

The superconducting properties and the pinning mechanisms of air-processed melt-textured grown Sm-Ba-Cu-O samples with the addition of small amounts of Pd (0.5wt%), Pt (0.5wt%) and CeO/sub 2/ (1.0wt%) were studied. The superconducting properties were enhanced by these additions, especially in co-doped samples. With co-doping of Pd/Pt or Pd/CeO/sub 2/, the samples exhibited a high T/sub c/ (/spl sim/91 K) and a high J/sub c/ (0 T,77 K)/spl sim/10/sup 4/ A/cm/sup 2/. Pinning forces vs magnetic field studies indicated that these samples have different pinning mechanisms from the un-doped sample. Observations of the microstructures showed that the Pt or CeO/sub 2/ addition reduced the sizes of the 211-particles significantly. EPMA results showed that the chemical distributions of these additions are different. Furthermore, TEM/EDS investigations found that the compositional fluctuation of the matrix in the sample co-doped with Pd/Pt is larger than in the sample co-doped with Pd/CeO/sub 2/.