Uranium chemistry and pinning centers in high temperature superconductor

A study has been made of compounds formed when up to 1% uranium oxide is added to YBa2Cu3O7-delta (Y123), prior to texturing. Initially, the study was to create pinning centers by addition of UO4, followed by neutron fission of some of the U-235 component. It was found that, prior to fission, the chemical reaction of U provides sufficient pinning centers to approximately double J(c). The U forms in deposits about 300 nm in diameter. The number of such deposits is proportional to the mass of U. TEM and XRD studies identify the compound as (U0.6Pt0.4)YBa2O6, a double perovskite. Neither T-c nor creep vary with %U. The uranium compound has also been produced outside of Y123. The behavior of uranium in high temperature superconductor (HTS) is thus of interest not only for introducing pinning centers by neutron fission of U but also as an effective chemical method to increase J(c). (C) 1998 Elsevier Science B.V., All rights reserved.