PREPARATION AND CRITICAL-CURRENT DENSITY OF HOT-PRESSED BI2SR2CA2CU3OX AG TAPES/

Bi2Sr2Ca2Cu3Ox (Bi-2223)/Ag tapes have been prepared by hot pressing p erformed at 800-840 degrees C for 12-96 h under 6 or 12 MPa in air. Th e highest transport critical current density, J(c), is 3900 A cm(-2) a t 77 K and 8800 A cm(-2) at 65 K under zero magnetic field, which is o bserved in tape hot pressed at 820 degrees C under 12 MPa for 24 h twi ce. The tape has undergone a cold pressing under 260 MPa between hot p ressings. J(c) is limited to 120 A cm(-2) in tape hot pressed for 48 h continuously, in spite of total hot pressing time, temperature and pr essure all being the same as for tape hot pressed for 24 h twice. It i s found that alternate hot pressing and cold pressing is effective in the preparation of Bi-2223 tapes with high J(c), which is determined b y the strength of grain coupling. Grain coupling is strengthened in ta pe hot pressed with an intermediate cold pressing. (C) 1998 Chapman & Hall.