CONTROL OF PARTIALLY MELTED MICROSTRUCTURE AND CRITICAL-CURRENT DENSITY FOR BI-2212 TAPES

Bi2Sr2CaCu2Ox (Bi-2212)/Ag tapes have been prepared using an isotherma l partial melting (IPM) method under controlled atmospheres, in which partial melting and solidification have been carried out at the same t emperature but under different atmospheres. Maximum critical current d ensity (J(c)) at 4.2 K under 0 T is 1.9x10(5) and 3.0x10(5) A/cm(2) fo r tapes prepared at 830 and 865 degrees C, respectively. This differen ce in J(c) is attributed to a microstructural difference. Bi-2212 grai n size can be controlled by melting temperature and both amount of imp urities and grain coupling strength can be controlled by solidificatio n time.