Improving CSD-Grown REBCO Thin Films by ACAC Addition to the Precursor Solution

Gd0.5Y0.5Ba2Cu3O7–x thin films have been grown from solutions of metal trifluoroacetates dissolved in methanol. These precursor solutions are well suited for chemical solution deposition because of their good wettability and long shelf lives. This could allow for high reproducibility of metalorganic decomposition and film growth if not counteracted by the highly hygroscopic nature of the solutions. Exposure to moist air can result in significant absorption of water with detrimental effects on microstructural film integrity, making the solutions and as-deposited films difficult to handle. To overcome this issue, acetylacetone (acac) has been introduced to the solutions as an additive. The complexing nature of this agent leads to strong interactions with the salts of Cu and the rare earth elements, reducing the sensitivity to humidity significantly. Films grown from acac-containing solutions are considerably smoother and denser, which in turn leads to enhanced current-carrying capabilities. To investigate the role of acac and its impact on the microstructure and superconducting properties of the films, infrared spectroscopy and thermogravimetry coupled with differential thermal analysis have been performed on different types of solutions and films with and without acac. The microstructural features of the films have been thoroughly compared by scanning electron microscopy. The superconducting properties, Tc and Jc, have been measured by inductive and resistive techniques. Particular focus has been put on the film characteristics that develop with varying amounts of moisture in the process gas during the decomposition of the metalorganic compounds.