Critical current limiting factors of hot isostatically pressed (HIPed) PbMo6S8 wires

摘要

PbMo6S8 wires with a molybdenum barrier and a stainless steel matrix were hot isostatically pressed (HIP) at 990°C and 1225°C for 4 hours at 110 MPa. The critical current density, its distribution, as well as the ac-susceptibility were investigated. The higher the applied HIP temperature, the better the critical current density becomes. A comparison of inductive Tc transitions suggests that HIPing is able to considerably reduce the width of the transition. In addition, at 1225°C, the Tc onset is shifted from 12.4 K to 14.2 K. The high field behavior of Jc strongly depends on the effective upper critical field which is essentially determined by grain boundaries. In a degraded wire sample, a qualitative correlation between effective upper critical field and the width of the inductive transition was found. This knowledge should allow to overcome the apparent limitation of Jc at high fields (2×108 Am-2 and 3×108 Am-2 at 20 T, 4.2 K and 1.8 K, respectively).