Fabrication and characterization of (Bi,Pb)-Sr-Ca-Cu-O (2223) bars
Bulk bars for current lead applications were fabricated from (Bi,Pb)-Sr-Ca-Cu-O (Bi-2223) for low thermal conductivity and high critical current. Bars measuring 17.8 cm in length were made by uniaxially pressing Bi-2223 powder of controlled (1.7/0.34)223 and (1,8/0.4)223 phase composition. The bulk bars were densified by subjecting them to a schedule of alternate liquid-phase sintering and cold isostatic pressing. Liquid-phase sintering temperatures were optimized from differential thermal analysis and microstructure morphology. Phase purity and microstructure were evaluated by X-ray diffraction and scanning electron microscopy. Low-resistance silver contacts were applied to the bars by hot-pressing at 820/spl deg/C and 3 MPa. Critical current densities /spl ap/1000 A/cm/sup 2/ (critical currents of 750 A at 77 K in self-field conditions) were achieved.