Effect of Growth Anisotropy on the Growth and Properties of RE123 Fabricated by Directional Solidification

RE123 (RE = Sm, Gd) superconductors were fabricated with directional solidification method in air. The effect of process parameters on continuous growth condition, growth anisotropy, and critical temperature (T_c) of solidified samples were investigated. In addition, the effect of Ag addition on those properties was also discussed. The maximum pulling rates for continuous growth are about 8 mm/h and 12 mm/h for Gd123 and Sm123, respectively. Although the highest rate decreased to about 2 mm/h for Gd123 and 4 mm/h for Sm123 by Ag addition, those rates were still about 5 times faster than that of Y123, and this is a merit for high production rate. On the other hand, the tilt angle of the ab-plane from the pulling axis did not show clear dependence on pulling rate in RE123 while the angle decreased with increasing the pulling rate in Y123. The Tc value of Sm123 increased as increasing the pulling rate. This might attribute to the difference in the Sm-Ba substitution; the degree of Sm-Ba substitution would be affected by the growth rates. The highest T_c of about 93 K was achieved in Sm123 with Ag addition.