Influence of Zr- and Sn-Doping on Sm-Ba-Cu-O Filaments Fabricated by a Chemical Solution Spinning

The effect of Zr and Sn addition on the critical current density (J_c) and the microstructure of filamentary SmBa₂Cu₃O_y (Sm123) has been investigated. Samples with additions fabricated by a solution spinning method were partially melted under an atmosphere gas containing 0.1-3.0% O₂. After heat-treatment, homogeneous dispersion of fine Sm₂BaCuO₅ (Sm211) particles was observed in the Zr-doped sample. The 0.2 at% Zr-doped Sm123 showed the depressed J_c value of 1.8 × 10⁴ at 77 K and self-field compared with the undoped sample. From the J_c measurement in magnetic fields, J_c value higher than 10³ A/cm² at 77 K was maintained up to 8 T. On the other hand, 0.2 at% Sn-added sample showed high J_c value of 5.0 × 10⁴ A/cm² at 77 K and self-field, and the J_c value higher than 10³ A/cm² is maintained up to 17 T. A small amount of Sn doping was found to be effective in increasing the J_c under high magnetic field and the irreversibility field of Sm123 filaments.