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 SmBa ₂Cu ₃O _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% O ₂. After heat-treatment, homogeneous dispersion of fine Sm ₂BaCuO ₅ (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 × 10 ⁴A/cm ² at 77 K and self-field compared with the undoped sample. From the J _c measurement in magnetic fields, J _c value higher than 10 ³A/cm ² 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× 10 ⁴ A/cm ² at 77 K and self-field, and the J _c value higher than 10 ³A/cm ² 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.