IMPROVED CRITICAL-CURRENT OF SUPERCONDUCTING BI2223-AG TAPES FOR CURRENT LEAD APPLICATION BY ADDITION OF LARGE SILVER PARTICLES

The effect of silver additions on the microstructure and superconducti ng properties of (Bi, Pb)(2)Sr2Ca2Cu3Ox (Bi2223)-Ag tapes has been inv estigated. We find a strong dependence on both the silver content and especially the silver particle size. The addition of small (5 mu m) pa rticles results in a slight reduction of the critical current. Large ( 400 mu m) particles are squeezed into long flat layers, leading to bet ter grain alignment, grain density and phase purity of the 2223 phase along these layers. As a consequence, the critical current is increase d by up to 60% in self-magnetic field, and even more in an external ma gnetic field.