The role of uranium, with and without irradiation, in the achievement of Jc ≈ 300000 A cm−2 at 77 K in large grain melt-textured Y123

The addition of uranium to large single grains of Y123 improves Jc prior to irradiation, by over 80%. Observations on the U chemistry and microstructure studies are presented. Irradiation with thermal neutrons, to fission the U235 component, results in further increases in Jc. Total increases of Jc by factors of, e.g. > 30 at 77 K, 0.25 Tesla, and > 20 at 50 K, 10.0 Tesla, result. Values of Jc of, e.g. 290000 A cm−2 at 77 K, 0.25 Tesla, and 1 million A cm−2 at 50 K, 0.25 Tesla, result. Tc is reduced by 0.5 K and creep rate is increased by 1/5. The chemical and irradiation effects are multiplicative and neither is yet optimized.