Kinetic Control of Ultrafast Transient Liquid Assisted Growth of Solution‐Derived YBa₂Cu₃O₇‐x Superconducting Films

Abstract Transient liquid assisted growth (TLAG) is an ultrafast non‐equilibrium growth process mainly governed by kinetic parameters, which are only accessible through fast in situ characterizations. In situ synchrotron X‐ray diffraction (XRD) analysis and in situ electrical resistivity measurements are used to derive kinetic diagrams of YBa₂Cu₃O_7−x (YBCO) superconducting films prepared via TLAG and to reveal the unique peculiarities of the process. In particular, diagrams for the phase evolution and the YBCO growth rates have been built for the two TLAG routes. It is shown that TLAG transient liquids can be obtained upon the melting of two barium cuprate phases (and not just one), differentiated by their copper oxidation state. This knowledge serves as a guide to determine the processing conditions to reach high performance films at high growth rates. With proper control of these kinetic parameters, films with critical current densities of 2–2.6 MA cm⁻² at 77 K and growth rates between 100–2000 nm s⁻¹ are reached. These growth rates are 1.5–3 orders of magnitude higher than those of conventional methods.