CRITICAL CURRENTS AND FLUX CREEP IN ORIENTATED BI-PB-SR-CA-CU-O 110 K-PHASE MADE BY THE POWDER IN TUBE METHOD

Critical currents, magnetic relaxation, magnetic irreversibility and microstructure have been studied for a (Bi,Pb)2Sr2Ca2Cu3Ox phase tape conductor fabricated by the powder in tube method. This conductor, with transport critical current density, Jct (at 77 K and O T), of a few thousand amperes per square centimetre and ab plane orientation to the rolling flat surface, showed pinning potential energies, Uo, of 66 meV for the field perpendicular to the ab plane and 181 meV for the field parallel to the ab plane; these values were much larger than those reported for the Bi2Sr2CaCu2Ox phase single crystal. Moreover, the field dependence of the magnetic irreversibility temperature was smaller for this tape conductor than that for Bi based crystals. These results imply an improvement in the pinning ability, due to the severe cold working peculiar to this process. Transmission electron microscopy (TEM) showed some defects, such as dislocations and twin-like structures, which may act as pinning centres. © 1990.