Melt processing and flux pinning of bulk RE-Ba-Cu-O high temperature superconductors

Recent advances in the processing of bulk RE-Ba-Cu-O (RE: rare-earth elements,REBCO) high-temperature superconductors are described. Different techniques, such asthin film seed crystals, top seeded melt growth (TSMG) and infiltration growth (IG)methods, and the modification of micro/nano structures have been developed to growlarge single-grained bulk superconductors with strong pinning centers at high fields.Reports show that these processing techniques led to the production of single-grainedREBCO superconductors > 10cm with trapped magnetic fields as high as 4T and 17T at77K and 29K, respectively, in a gap between two pieces of Y-Ba-Cu-O single-grainedmaterial. The significant enhancement of Jc (H,T) is found in REBCO bulks with theaddition of nano-scaled precursors. Microstructure analysis revealed that the crystallinedefects, which are related to dl pinning at low magnetic fields and the nano-scale periodicstructures, which are related to the field induced dTc pinning centers at high magneticfields are observed in the REBCO bulks with the addition of nano-scaled precursors. Inaddition, the dR/dT of Resistivity - Temperature -Magnetic field (H) curves exhibitedtwo peaks, showing that there are two types of effective pinning mechanisms at differentmagnetic fields, respectively.