The achievement of high growth rates in YBa 2 Cu 3 O 7 epitaxial high-temperature superconducting films has become strategic to enable high-throughput manufacturing of long length coated conductors for energy and large magnet applications. We report on a transient liquid assisted growth process capable of achieving ultrafast growth rates (100 nm s −1) and high critical current densities (5 MA cm −2 at 77 K). This is based on the kinetic preference of Ba-Cu-O to form transient liquids prior to crystalline thermodynamic equilibrium phases, and as such is a non-equilibrium approach. The transient liquid-assisted growth process is combined with chemical solution deposition, proposing a scalable method for superconducting tapes manufacturing. Additionally, using colloidal solutions, the growth process is extended towards fabrication of nanocomposite films for enhanced superconducting properties at high magnetic fields. Fast acquisition in situ synchrotron X-ray diffraction and high resolution scanning transmission electron microscopy (STEM) become crucial measurements in disentangling key aspects of the growth process.

A B S T R A C TThe processes involved in the thermal decomposition of yttrium propionate in oxidizing and inert atmosphere were analyzed with thermoanalytical techniques (thermogravimetry and evolved gas analysis) and with the help of structural characterization (X-ray diffraction, infrared spectroscopy and elemental analysis) of intermediate and final products. Samples in the form of films and powders were analyzed. The decomposition behavior studied as a function of particle size and film thickness was investigated. We conclude that, as a consequence of the gas and heat transport, films decompose differently than powders. Finally, two decomposition mechanisms are proposed that are in agreement with the observed volatiles and intermediate phases.

Film and powder samples from a BaAc2 solution in propionic acid/MeOH were decomposed in different atmospheres and their thermal decomposition was characterized by means of thermogravimetry coupled with evolved gas analysis techniques (TG-FTIR, EGA-MS) and chemical and structural methods (EA, XRD, FTIR). The thermal behavior of the films was found to be different than the corresponding powder, in terms of volatiles, kinetics, intermediate phases and purity of final product. The mixed Ba-Prop-Ac salt obtained from solution decomposes to BaCO3 before 400°C through oxidative degradation, and above 400°C in inert atmosphere through a radical path releasing symmetrical ketones. Its double melting behavior is also highlighted and its decomposition understood by comparison with BaProp2 and BaAc2 precursors, and put into context of YBa2Cu3O7-∂ (YBCO) film pyrolysis.