Among high temperature superconductors (HTS), YBa₂Cu₃O₇ (YBCO) films and coated conductors (CCs) offer an unparalleled opportunity to be used in large scale superconducting power applications and high field magnets due to their outstanding ability to carry high currents at high magnetic fields. However, there is a crucial need of high performance, high throughput, and low cost manufacturing of CCs. Chemical solution deposition (CSD) has become a very competitive cost-effective and scalable methodology to produce epitaxial thin films, with enhanced performance at high magnetic fields by the incorporation of secondary phase nanoparticles (NPs) [1]. However, their growth rates are rather small (0.5-1 nm/s). In this regard, we have developed a novel growth approach, entitled, Transient Liquid Assisted Growth (TLAG) [2], which is able to combine CSD methodologies for fluorine-free metalorganic precursors with ultra-fast growth rates (100 nm/s) by facilitating a non-equilibrium liquid-mediated approach (consisting of Ba-Cu melts) and several intermediate reactions (e.g., RE ions dissolve and diffuse at ultra-high speeds), being compatible with nanocomposite and CCs growth. Critical current densities up of 5 MA/cm² at 77K are already realized in TLAG-CSD grown YBCO thin films. The recent progress in TLAG-CSD, in terms of microstructure, growth mechanisms, and growth rate, will be presented. Moreover, an additional advantage of TLAG-CSD is that preformed NPs can be incorporated to the metalorganic ink to prepare superconducting nanocomposites with enhanced vortex pinning. The microstructure of pyrolyzed and grown YBCO thin films along with new defects landscape at the atomic level using different techniques of scanning transmission electron microscopy (STEM) will also be presented. Finally, the potential of TLAG-CSD for industrial scaling up and the approaches followed to grow thick coated conductors will be discussed.

[1] J. Gutierrez, A. et al., Nat. Mat., 6, 367 (2007)
[2] L. Soler et al, Nat. Commun., 11, 344 (2020)

Fig. STEM images of, TLAG-CSD YBCO films indicating the different microstructures for a) 0.4 ºC/s, (b) 20º/s, highlighting the tunability for vortex pinning,  (c) a 12% BZO nanocomposite, where inset shows that BZO NPs grow epitaxial with the YBCO matrix contrary to the other CSD processes [2].

Keywords: YBCO, TLAG-CSD, TEM, Superconductivity