Surface Acoustic Waves—A New Thin-Film Deposition Approach for Coated Conductors
A new approach for the deposition of layers for coated conductors has been developed. High-frequency surface acoustic waves (SAWs) were applied for the atomization of precursor solutions into an ultrafine aerosol. The deposition via aerosol droplet condensation offers several advantages over existing deposition methods including ink jet printing and dip coating, e.g., a variable droplet size and the possibility of gel condensation in the aerosol phase due to solvent evaporation. In the future, a combination of two or more SAW atomizers might enable the simultaneous deposition of separate solutions and even nanoparticle dispersions. First, experiments were performed using water-based and propionic-acid-based mixed lanthanum and zirconium precursor solutions. These solutions are supplied to a SAW device via a stainless steel capillary, leading to continuous aerosol production. The aerosol droplets of the precursor solution were deposited on biaxial textured Ni-5 at.%W tapes having an area of 1-cm width and about 5-cm length and were subsequently crystallized into a continuous thin La2Zr2O7 buffer layer in a tube furnace. X-ray diffraction studies showed that the La2Zr2O7 films have high crystalline quality with a strong (001)-orientation. Furthermore, microstructural analysis on the deposited films showed homogeneous and dense layers.