Fluorine-free sol gel deposition of epitaxial YBCO thin films for coated conductors

Abstract

The current trend of coated conductor development has motivated an increasing need for a novel synthesis route by which a highly epitaxial YBCO film can be readily deposited on buffered substrates. It has been demonstrated that the fluorine-based sol gel approach can produce high quality, epitaxial YBCO thin films that exhibit a superconducting J c of over 3–5 MA/cm 2 in self-field, 77 K. In this study we have developed a new fluorine-free sol gel approach (FFSG) as an effective alternative. The advantages of this new approach is three-fold: (1) no HF during the processing that is detrimental to the film; (2) the FFSG solution is much less reactive to the buffer layer, and (3) the microstructure of the YBCO thin film is more uniform and denser than achieved by the fluorine-based method. Using the new FFSG method, the YBCO thin films have been deposited on the LAO substrates. A high J c on the order of 5 × 10 5 A/cm 2 at 77 K and self-field has been reported. Experimental results on film synthesis, and superconducting properties are presented.