Controlled crystal orientation in fluorine-free superconducting YBa2Cu3O7−δ films

Abstract

The opportunity to control crystal orientation is a serious benefit in the multidisciplinary application field of YBa2Cu3O7−δ (YBCO) thin films. c-Axis aligned YBCO thin films are used in cable industry, while a-axis alignment is required for Josephson junctions. Within this study, we succeeded to control the crystal orientation in fluorine-free YBCO thin films obtained by chemical solution deposition (CSD). Using a direct annealing process, a c-axis aligned YBCO thin film was obtained. In order to increase the flexibility of incorporation into an industrial approach, a preceding burn-out step was introduced. After the introduction of a burn-out process, a-axis oriented films were obtained. If however, CO2 was added during heating towards the annealing temperature, c-axis aligned films were achieved. These observations were linked to the corresponding reaction mechanism leading to an explanation of this orientation alignment. Using the CO2 controlled process, an YBCO thin film with a Tc,onset of 92K and a Jc of 1.25MAcm−2 was obtained. Sustainable YBCO films were therefore generated from a fluorine-free water-based precursor.