FABRICATION AND CHARACTERIZATION OF (BI,PB)-SR-CA-CU-O-(2223) BARS

Bulk bars for current lead applications were fabricated from (Bi,Pb)-S r-Ca-Cu .. O (Bi-2223) for low thermal conductivity and high critical current. Bars measuring 17.8 cm in length were made by uniaxially pres sing 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 sch edule of alternate liquid-phase sintering and cold isostatic pressing. Liquid-phase sintering temperatures wc:re optimized from differential thermal analysis and microstructure morphology. Phase purity and micr ostructure were evaluated by X-ray diffraction and scanning electron m icroscopy. Low-resistance silver contacts were applied to the bars by hot-pressing at 820 degrees C and 3 MPa. Critical current densities ap proximate to 1000 A/cm(2) (critical currents of 750 A at 77 K in self- field conditions) were achieved.