Directionally solidified REBa2Cu3O7−x (RE=Y, Gd, Sm...: RE123) superconductive oxides are expected for high magnetic field applications such as the superconducting current lead. In this study, the Y123 thin fibers with a diameter of about 0.5 mm were directionally solidified with several pulling rates, and transport current properties were evaluated at 77 K. The continuous growth of Y123 single domain crystal was obtained up to the pulling rate of 2.8×10-6 m/s or less under the temperature gradient of 26 K/mm in the thin fibers while such the structure was obtained only up to the pulling rate of about 5.6×10-7 m/s in usual φ2 mm rods. This increase in the limit of the maximum pulling rate, at which the continuous growth is obtained, could be explained by the suppression of Y123 nucleation since the volume of the undercooled liquid ahead of the growth interface is small in the thin fibers. In addition, the large temperature gradient at the growth interface will be the important factor to supply the necessary solute for the Y123 crystal growth. The high Ic value of 134 A, and corresponding Jc of 1.0×109 A/m2, was achieved in the thin fiber grown at R =1.7×10-6 m/s. This suggests that the directionally solidified thin fiber has the advantage to attain both the high production rate and the high Jc properties.
