Fabrication and transport current properties of directionally solidified Y123 thin fiber

In this paper, the effect of fabrication conditions on the microstructure and transport J_c properties of thin Y123 fibers were investigated. Fibers with 0.5 mm in diameter were directionally solidified by a zone melting method. The continuous growth structure was achieved in the samples grown at high pulling rates up to 10 mm/h, and the size of trapped Y211 particles was decreased with increasing pulling rate. The transport J_c values were maximum in the sample pulled at 6 mm/h, and the best I_c and corresponding J_c values achieved were 134 A and 1×10⁵ A/cm² at 77 K self-field, respectively. Since the ab-plane of the Y123 crystal is reported to align parallel with the longitudinal direction of the sample grown at high pulling rate, this high J_c value was associated with this preferential crystal orientation as well as fine Y211 particles. Further increase of the pulling rate, however, resulted in the degradation of the crystallinity of the Y123, and the J_c values were decreased. The suppression of the formation of sub-domain structure and the preservation of better crystal orientation are therefore required to attain a high J_c value.