Very large superconducting currents induced by growth tailoring

Abstract

The efforts of carrying forward superconducting materials to commercialization can be overcome by materials with high performance potentiated by a suitable processing technique. In this work, extreme critical currents up to 241 A @ 77 K were attained by tuning the crystal growth in a directional solidification process. Bulk rods of textured Bi-2212/2.9 wt % Ag were obtained by changing the conventional laser floating zone technique through the application of a d.c. electrical current during the crystallization process. Using an optimized composition, the electrically assisted laser floating zone (EALFZ) allowed obtaining 5800 A/cm2 in rods exhibiting only 2.3 mm in diameter, the highest value reported so far for bulk samples. This behavior is a consequence of the texture enhancement and radial phase distribution, exceeding a 2-fold increase in Jc compared with samples grown without electrical current. Morphological and structural observations are discussed and correlated with the results from the electrical characterization. Applications on extremely efficient electrical current leads working at temperatures below 77 K using the above-described materials grown by EALFZ are anticipated.