Critical current limiting factors of hot isostatically pressed (HIPed) PbMo/sub 6/S/sub 8/ wires

PbMo/sub 6/S/sub 8/ wires with a molybdenum barrier and a stainless steel matrix were hot isostatically pressed (HIP) at 990/spl deg/C and 1225/spl deg/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 T/sub c/ transitions suggests that HIPing is able to considerably reduce the width of the transition. In addition, at 1225/spl deg/C, the T/sub c/ onset is shifted from 12.4 K to 14.2 K. The high field behavior of J/sub c/ 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 J/sub c/ at high fields (2/spl times/10/sup 8/ Am/sup -2/ and 3/spl times/10/sup 8/ Am/sup -2/ at 20 T, 4.2 K and 1.8 K, respectively).<
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