Improving the critical current density in Bi-2223 wires via a reduction of the secondary phase content

Progress in the performance of multifilamentary composite Bi-2223 wire fabricated at American Superconductor is reviewed. Critical current (I/sub c/) performance of 175 A at 77 K and self-field and critical current density (J/sub c/) performance of 22.1 kA/cm/sup 2/ (77 K, 0.1 T perpendicular to the tape plane) have been measured for short samples of Bi-2223 wire (standard size is 0.21/spl times/4.0/spl times/100 mm). Microstructure analysis by SQUID magnetometry, transmission XRD and TEM shows a large amount of residual 2212 intergrowth remaining in Bi-2223 grains. Residual 2212 intergrowth is seen to correlate with self-field J/sub c/ at 77 K across a range of experimental samples, suggesting that higher levels of performance will be achieved by further reducing residual 2212.