Mechanical and critical current characteristics of high-strength (Bi, Pb)₂Sr₂Ca₂Cu₃O_10+δ tapes under uniaxial tensile strain

We investigated the mechanical properties and superconducting characteristics of high-strength (Bi, Pb)₂Sr₂Ca₂Cu₃O₁₀+δ tapes reinforced by Ni-based alloy lamination over a wide range of temperature (30 K≤T ≤ 300 K), magnetic field (B ∥ c ≤ 6 T), and uniaxial tensile strain (ε ≤ 0.6%) conditions. We found that the Young’s modulus evaluated from the stress–strain curves increases gradually with decreasing temperature (120 GPa at 300 K and 142 GPa at 40 K), indicating the importance of low-T data for designing high-field magnets. The enhancement of the Young’s modulus of the tape at such low temperatures is probably attributable to the use of a Ni-based alloy for reinforcement and is also reflected in the irreversible stress. The critical current, I_c, measured under various (T, B, ε) conditions decreases almost linearly with uniaxial tensile strain in the reversible region. We constructed a phenomenological model of I_c(T, B, ε) that can roughly reproduce the observed I_c under all the (T, B, ε) conditions we investigated. We expect that fine adjustment of the model parameters based on more detailed measurements will make it possible to estimate I_c(T, B, ε) under arduous measurement conditions from data obtained under conditions where measurement is relatively easy.