Irreversibility Lines and Critical Currents in Neutron Irradiated MPMG YBa2Cu3O7-δ Superconductors
Two “Melt-Powder-Melt-Grown” YBa2Cu3O7-δ samples were prepared, oriented and analyzed by optical and x-ray methods. The first sample contains 12.8 wt% of the 211-phase and 4.7 wt% of metallic silver, the second 17.5 wt% 211 and 7.4 wt% silver. The samples were investigated by ac susceptibility and by the flux profile technique to evaluate the critical current densities. The samples were repeatedly irradiated with fast neutrons to fluences ranging from 2·1021 to 6·1021 m−2 (E003E0.1 MeV). As observed on single crystals, Jc shifts to higher values. However, the enhancement factors are not particularly high (~10) and vary with temperature in a rather unusual way. A small “fishtail” effect measured on the unirradiated samples at various temperatures disappears after neutron irradiation. The irreversibility lines (IL) do not show strong enhancements upon neutron irradiation. For H||c the IL increases, whereas slight decreases are observed for Blab. This behavior of the IL was observed on both samples. The fluence dependence of Jc and the IL’s is compared with results obtained on single crystals.
KeywordsHigh Temperature Superconductor Critical Current Density Neutron Irradiation Metallic Silver Flux Line
Unable to display preview. Download preview PDF.
- J.D. Jorgensen, B.W. Veal, A.P. Paulikas, L.J. Nowicki, G.W. Crabtree, H. Claus, and W.K. Kwok, Structural properties of oxygen deficient YBa2Cu307, Phys. Rev. B 41:1863 (1990).Google Scholar
- 8.M. Murakami, “Melt Processed High-Temperature Superconductors”, World Scientific, Singapore/New Jersey/London/Hong Kong (1992).Google Scholar
- 9.A.M. Campbell, The response of pinned flux vortices to low frequency fields, J. Phys. C 2: 492 (1969)Google Scholar
- 10.H. Kupfer, C. Keller, R. Meier-Hirmer, K. Salama, V. Selvamanickam, and G. Tartaglia, Critical current and relaxation of oriented grained YBa2Cu307 after neutron irradiation, IEEE Trans. Magn. MAG-27: 1369 (1991)Google Scholar
- 11.H.W. Weber and G.W. Crabtree, Neutron irradiation effects in high Tc single crystals, in: “Studies of High Temperature Superconductors”, A.V. Narlikar, ed., Nova Science Publishers, New York 9:37 (1992)Google Scholar
- 12.M.A. Kirk and H.W. Weber, Electron microscopy investigations of irradiation defect structures in the high Tc superconductor YBa2Cu307_„, in: “Studies of High Temperature Superconductors” A.V. Narlikar, ed., Nova Science Publishers, New York 10:253 (1992)Google Scholar
- 13.M.C. Frischherz, M.A. Kirk, J.P. Zhang, and H.W. Weber, Transmission electron microscopy of defect cascades in YBa2Cu307 produced by ion irradiation, Phil. Mag. A 67: 1347 (1993)Google Scholar
- 14.M.C. Frischherz, M.A. Kirk, J. Farmer, L.R. Greenwood, H.W. Weber, Defect cascades produced by neutron irradiation in YBa2Cu307, submitted to Phil. Mag. B Google Scholar