Electron beam co-evaporation of Y-BaF₂-Cu precursor films for YBa₂Cu₃O_7-y coated conductors

Y-BaF₂-Cu precursor films for Y-Ba₂Cu₃O_7-y (YBCO) coated conductors have been deposited on both uncoated nickel and Rolling Assisted Biaxially Textured Substrate (RABiTS™) tapes by electron beam coevaporation. The water partial pressure was kept constant at 1 × 10^-5 Torr during the deposition in order to control the oxygen content in the precursor films. Rutherford backscattering spectroscopy measurements indicate an average composition of Y:Ba:Cu of 1.05:2.10:3.0 with a standard deviation of less than 2.0%. This result was obtained for both moving and stationary tapes. The thickness variation of such precursor films is less than 2.5% over lengths of up to 1 m. Films up to 5 μm thick have been deposited on a stationary tape. An end-to-end J_c of 100000 A cm^-2 from a 1 m length of RABiTS™ sample has been obtained with the highest J_c of 774000 A cm^-2 in a short section within the tape. The present research demonstrates a possible route for industrial scale-up using electron beam coevaporation of YBCO precursors.