MICROSTRUCTURAL INVESTIGATIONS OF AG BI(PB)SRCACUO TAPES PREPARED USING COMMERCIAL-GRADE MATERIALS/

Self-field critical current density (J(c)) data on Ag-clad Bi1.7Pb0.4S r1.8Ca2Cu3.5Ox tapes prepared using low-purity commercial-grade (98-99 %) starting materials are presented. J(c) is found to be increasing wi th decreasing core thickness. Tapes with a 7 mu m thick core and prepa red with repeated rolling and sintering have J(c) = 6.14 X 10(3) A cm( -2) at 77 K and 1.49 X 10(5) A cm(-2) at 4.2 K. TEM investigations on these tape specimens reveal a number of microstructural features which might be acting as nux-pinning sites and might thus be responsible fo r J(c) values higher than for corresponding tapes prepared with high-p urity (99.99%) materials.