The presence of impurities in the precursor metal carboxylate solutions for the preparation of epitaxial thin films by metal organic decomposition (MOD) is substantially avoided by the use of acid anhydrides. In particular, trifluoroacetic anhydride (TFAA) was used for the synthesis of the starting Y, Ba and Cu trifluoroacetates used in YBa2Cu3O7−x (YBCO) preparation by the MOD process. In this way, highly stable organometallic precursors and a short pyrolysis process could be used leading to YBCO films with high critical currents (Jc ≥2–4 MA cm−2 at 77 K). Furthermore, the reproducibility of the results has been ascertained.

The achievement of low cost deposition techniques for high critical current YBa 2 Cu 3 O 7 coated conductors is one of the major objectives to achieve a widespread use of superconductivity in power applications. Chemical solution deposition techniques are appearing as a very promising methodology to achieve epitaxial oxide thin films at a low cost, so an intense effort is being carried out to develop routes for all chemical coated conductor tapes. In this work recent achievements will be presented towards the goal of combining the deposition of different type of buffer layers on metallic substrates based on metal-organic decomposition with the growth of YBa 2 Cu 3 O 7 layers using the trifluoroacetate route. The influence of processing parameters on the microstructure and superconducting properties will be stressed. High critical currents are demonstrated in 'all chemical' multilayers.

The mechanisms controlling stress relief during the drying and pyrolysis processes of trifluoroacetate metal-organic precursors have been elucidated in view of high rate fabrication of epitaxial superconducting YBa2Cu3O7 thin films. Combining FTIR, TGA, and film thickness evolution measurements, we conclude that gel drying and sintering occurs below T ∼ 250 °C while film densification, due to metal-organic pyrolysis, occurs in the range 250−310 °C. Stress relief is the driving force leading to smooth or structurally inhomogeneous films, displaying buckling or macrocracks, depending on the rate of film transformation. High heating rates can be used during the gel drying and sintering process preserving the film homogeneity because the developed stress is below that required to generate buckling, as demonstrated by nanoindentation experiments. Within the temperature window where the metal-organic decomposition process occurs, the gas flow and the temperature ramp can be tuned to achieve fast pyrolysis preserving the film homogeneity. Optical microscopy, TEM, SEM, AFM, nanoindentation, μ-Raman spectroscopy, electrical resistivity, and critical current measurements of the films have been combined to stress the relevance of preserving the homogeneity of the films from the nanometric to the macroscopic length scales, to achieve high critical current YBa2Cu3O7 thin films, i.e., J c ≈ 3−4 MA/cm2 at 77 K.

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