Novel technique for improving field dependence in Bi-2223 superconducting tapes at 77 K

In order to use Bi₂Sr₂Ca₂Cu₃ O_y (Bi-2223) superconducting tapes for practical applications at liquid nitrogen temperatures, the critical current density (J_c) must be as high as possible under an applied magnetic field. In this work, an attempt was made to increase pinning in Bi-2223 superconducting tapes by creating defects at the interface between a Bi-2223 superconductor and an MgO single crystal. Reference samples showed decreased I_c values at 77 K in a 0.4 T field applied perpendicular to the width of the tape to ≈4 to 7% of the I _c value in zero field. With improved pinning, the I_c value in the field decreased to 12 to 20% of the I_c value in zero field. Results were compared with in-field performance of high-quality coated YBa₂Cu₃O_Y (Y-123) tapes, which showed an in-field decrease to ≈30% of the I_c value in zero field