抄録
In the production of melt-textured RE-Ba-Cu-O bulk superconductors, the precursors are generally prepared by uniaxial and/or cold-isostatic pressing of raw powders. The employment of fine starting powders is effective in fabricating high-performance RE-Ba-Cu-O bulk superconductors. However, cracks often form in the green bodies when fine powders are unaxially pressed. In this work, we have investigated the defects in green bodies during the powder compression process for bulk superconductor fabrication. Fine and large YBCO powders and granulates of binder-added fine powder were uniaxially pressed into tablets (20 mm in diameter) using 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 cracks on the parallel in the direction of pressing were found in green bodies. These defects in green bodies partially remained after melt-processing and affected the field-trapping abilities of melt-textured bulk samples. The addition of an organic binder is very effective method for reducing defects in green bodies.
