The growth of Chemical Solution Deposition (CSD) nanocomposites from precursor solutions containing metal preformed nanoparticles has recently proven to be a very good pathway developing low cost YBa₂Cu₃O_7-δ (YBCO) superconducting layers carrying high currents at high magnetic fields by pinning vortices at none superconducting nanoscale defects [1][2].

In our work, we are able to synthesize binary metal oxide NPs using a 2 steps process called hybrid hydrolytic-solvothermal synthesis (H2S2). In the presence of a polyol as surfactant, we have synthesized small-sized, crystalline, monodisperse and stable BaMO₃ NPs (M= Zr, Hf). We are able to tune their size in a range of 4 - 20 nm, controlling the hydrolysis step involved in the reaction mechanism [3]. On the other hand, combine H2S2 process with a post-synthetic surface functionalization we have obtained, for the first time, small-sized (4-6 nm) and agglomeration-free BaM₂O₆ NPs (M= Nb, Ta).

These NPs are being used for the preparation of superconducting nanocomposites using the non-equilibrium ultrafast Transient Liquid Assisted Growth (TLAG-CSD) process. We have developed a fluorine-free functional colloidal ink adapted to TLAG-CSD nanocomposites able to achieve very homogenous and reproducible multideposited films. We have demonstrated the compatibility and stabilization of the colloidal ink, obtaining homogenous pyrolyzed films with crystalline NPs, homogenously distributed without coarsening. Finally, we have further proved the compatibility and chemical/thermal stability of NPs with the TLAG approach [4] and through In-situ synchrotron X-ray diffraction we determined the kinetic process parameters strongly influencing the TLAG growth process. The kinetic phase diagrams developed from In-situ XRD experiments [5] have allowed us to achieve epitaxial YBCO multideposited TLAG nanocomposites obtaining Jc results of 2-2.5 MA/cm² at 77 k for 400 nm of thickness with smooth Jc(H) curves provided by NP pinning at the fast growth rates of even 1300 nm s^-1.

[1] A. Llordés et al., Nat Mater. 6, 2012, 329-36
[2] Z. Li et al., Scientific Reports 9, 2019, 5828
[3] N. Chamorro et eal., RSC Adv. 10, 2020, 28872-28878
[4] L. Soler et al., Nat Commun. 11, 2020, 344
[5] S.Rasi et al., Adv.Sci. 2022, 2203834

Keywords: Superconducting Nanocomposite Films , Colloidal Inks , Chemical Solution Deposition, Transient Liquid Assisted Growth