Progress in the Continuous Depostition of YBCO Coated Conductors by Thermal Co-Evaporation

Abstract

We report on recent progress towards the continuous deposition of YBCO Coated Conductors (CC) by thermal co-evaporation. This is an attractive vacuum technique thanks to the simplicity, low cost and intrinsic uniformity over large areas. Recently, we published the in situ preparation route of 1 μm thick superconducting YBCO films deposited onto CeO2 buffered Ni biaxially textured tapes using a reel-to-reel system; end-to-end critical current densities Jc's at 77 K and self-field, measured by transport measurements are in the 1-2 MA/cm2 range for 1 m. long samples, with zero-resistance Tc= 87 K and transition widths DTc<3 K. In spite of the very good CC’s performances reported by a number of laboratories all over the world, several steps must be optimized in order to limit the CC production costs, in particular concerning the complexity of the CC architecture and the choice and optimization of the YBCO deposition technique. We specifically address the following critical points regarding: 1) the in situ oxidation of the YBCO layer using a novel supersonic nozzle, 2) the deposition by thermal or e-beam evaporation of thick crack-free CeO2 buffer layers and 3) the scaling-up of the deposition process using a new multichamber system.