Critical current distribution of hot isostatically pressed PbMo₆S₈ wires

The PbMo₆S₈ Chevrel phase has an important potential for the construction of ultra-high-field superconducting coils. The ritical current density of hot isostatically pressed (HIP) PbMo₆S₈ wires with a stainless steel matrix and a molybdenum diffusion barrier was investigated in fields up to 25 T. The field dependence of Jc is considerably improved in the high-field regime by going from a 990°C, 4 h to a 1225°C, 4 h HIP treatment at 110 MPa. However, a drop of Jc at unusually low fields as 15 T was observed. The appearance of a double peak in the critical current distribution, obtained by dV²/dI² suggests that the origin of such a behavior is a strongly reduced effective upper critical field B∗c2, presumably at grain boundaries. A detailed analysis of the critical current distribution reveals that only a few percent of the wire is in a dissipative state at an electric field criterion of 1 μ V cm⁻¹, indicating that the used HIP parameters are not yet optimized