Formation of defects in precursors for melt-textured RE-Ba-Cu-O superconductors and effect of organic binder addition

On the processing melt-textured RE-Ba-Cu-O bulk superconductors, we investigated the formation of defects in green bodies during powder compression process and the effect of the defects on the final bulk products. Two kinds of Y-Ba-Cu-O powders with fine and large particle sizes and the granules of binder-added fine powder were uniaxially pressed into tablets (20 mm in diameter) under different pressures from 31 to 125 MPa. When the fine powder was pressed at pressures above 62 MPa, several defects such as lamination, capping and vertical cracking were found in green bodies. The defects in green bodies partially remained after melt-processing and lowered the field-trapping abilities of melt-textured bulk samples. The addition of organic binder is very effective method to reduce the defects in green bodies.