Insights into the effect of Ti doping on Nb₃Sn superconductors

Ti doping is a common method for improving the critical current density (J_c). However, Ti is always incorporated in a designated region (Cu–Sn matrix or Nb core), ignoring the intrinsic distribution characteristic of Ti as a raw material. Moreover, the optimal doping amount of Ti was ambiguous. Therefore, in this work, the effect of Ti on the microstructures and superconducting properties of the Nb₃Sn superconductor was systematically investigated using the powder metallurgy method. The results showed that Ti doping could increase the average Sn content and reduce the concentration gradient of Sn in the Nb₃Sn layer. In addition, the grains of Nb₃Sn were appropriately refined. On such a basis, the irreversible field (B_irr) and the pinning force density (F_p) and, thereby, the critical current density (J_c) at high magnetic fields were substantially affected by Ti doping. Specifically, the 1 at.%Ti-doped sample exhibited the best performance, and its J_c reached 2.09 × 10⁸ A/m² at 8 T.