FURTHER-STUDIES ON AG BPSCCO TAPES USING LOW PURITY MATERIALS/

Transmission electron microscopic (TEM) studies are reported on Ag-cla d Bi1.7 Pb0.4Sr1.8Ca2Cu3.5Ox tapes prepared by using low purity (98-99 %) commercial grade materials. The self-field J(c) values of these tap es viz. 6.14 x 10(3) A.cm-2 at 77 K and 1.4 x 10(5) A.cm-2 at 4.2 K, r eported in an earlier publication, were significantly higher than the corresponding J(c) values in tapes prepared with high purity (99.99%) materials. The TEM pictures on the low purity core material of the tap es reveal the presence of stacking faults and the intergrowth of the 2 212 and 2223 phases which could be acting as flux pinning sites and re sponsible for enhanced J(c) values. These defects can perhaps be trace d back to the presence of 60 ppm iron in the low purity CuO as reveale d by atomic absorption analysis reported earlier.