Periodic Reporting for period 4 - ULTRASUPERTAPE (ULTRAfast growth of ultrahigh performance SUPERconducting TAPEs) Reporting period: 2020-06-01 to 2022-05-31 Summary of the context and overall objectives of the project ULTRASUPERTAPE aimed to demonstrate an unprecedented approach for fabrication of low cost / high throughput / high performance High Temperature Superconducting (HTS) tapes, or Coated Conductors, to push the emerging HTS industry to market. The breakthrough idea was the use of Transient Liquid Assisted Growth (TLAG) from low cost Chemical Solution Deposition of Y, Ba, Cu metalorganic precursors to reach ultrafast growth rates. The key concept relied on the discovery of the mechanisms for the decomposition of barium carbonate and the non-equilibrium kinetic growth through the transient liquid formation even for thick films via fast heating or fast PO2 step. The use of synchrotron x-ray diffraction for the analysis of the in-situ growth process at fast acquisition times was essential. ULTRASUPERTAPE succeeded to boost Coated Conductor growth rate up to outstanding limits while high performances at low and high magnetic fields were reached, by smartly designing and engineering the local strain and electronic state properties of nanocomposite superconducting films prepared from nanoparticle colloids. Innovative Additive Manufacturing and Digital Printing methodologies were combined with combinatorial chemistry to fabricate gradient compositional samples and data were used in machine learning algorithms for fast screening process conditions. In collaboration with two ERC-PoC grants, IMPACT and SMS-INKS, an integrated system capable of addressing the entire fabrication process, from solution synthesis, deposition, ultrafast epitaxial crystallization of the superconducting phase, market assessment and explotation plan will be available. A trade secret and a patent have been filed and first technology transfer actions were already executed. Wise ideas and technology are emerging from the TLAG process promoting long length and large area production or localized fast growth of functional epitaxial films or multilayer structures. We are excited to enter the market with TLAG and collaborate in the new energy paradigm with innovative superconducting solutions. Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far During these 78 months, ULTRASUPERTAPE has advanced in the knowledge of the new Transient Liquid Assisted Growth (TLAG) process for the preparation of High Temperature Superconducting tapes. This knowledge has been gathered from the hard work of a very motivated and enthusiastic team. Major scientific achievements include: 1) Unique metalorganic colloidal inks for the homogeneous thick deposition of the chemical solution layers up to 3 µm (patend filed). 2) Demonstration of ultrahigh growth rates with two independent growth approaches reaching even 2000 nm/s. 3) Reproduible and highly epitaxial layers have achieved by proper control of the supersaturation conditions of the liquid-based process reaching 2.5^-4 MA/cm2 at 77 K for film up to 0.5 µm in thickness (trade secret filed). 4) Identification of the kinetic growth mechanism and reaction paths, definition of the kinetic phase diagrams and the existence of Ba-Cu-O transient liquids of different Cu oxidation state. 5) TLAG growth of epitaxial nanocomposites with high performances using non-reactive BaZrO3 and BaHfO3 nanoparticles of small sizes (7 nm). 6) TLAG was implemented on industrially reliable substrates overcoming the reactivity associated to the Ba-Cu-O liquid. 7) A robust CSD solution with a very low cost production procedure giving very homogeneous and low porosity pyrolysis, also compatible with thick layers and scalable deposition printing techniques. 8) A methodology based on combinatorial chemistry and data analysis was developed to fast screen growth parameters and compositions. 9) Correlation of vortex pinning and microstructure landscape for TLAG films. 10) First technology transfer actions were initiated with HTS fabrication companies. Overall during ULTRASUPERTAPE, 79 oral/invited talks were given, 21 articles were published, 1 patent was filed, 2 ERC-PoC awards were granted and 34 outreached actions were disseminated, 6 synchrotron experiment beamtime campaigns were executed (4 in Soleil, Paris and 2 in ALBA, Barcelona). Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far) ULTRASUPERTAPE has generated a disruptive high throughput technology to prepare High Temperature Superconducting Coated Conductors with ultrahigh performance to be used in ultrahigh field magnets and energy power applications. Magnets in the range of B>30 T can only be fabricated with HTS while the cost/performance ratio required for electrical power applications can only be reached if a high throughput (high production rate and a low cost) manufacturing technology is achieved. ULTRASUPERTAPE has created disruptive solutions to the materials engineering requirements of superconducting tapes with a quantum leap in cost/performance ratio (about a factor 4-5). The intrinsic low cost of chemical solution deposition (CSD) methodologies, as compared to other approaches intensive in capital investment or in expensive chemicals, assures a high gain / high risk balance of the novel methodology. This novel approach is expected to bring European competitiveness well beyond the major industrial producers worldwide. ULTRASUPERTAPE has already demonstrated the ultrafast growth rate over 1000 times faster than present technologies (with the consequent reduction of production cost) and its compatibility with low cost CSD additive manufacturing methodologies for high performance films. In addition, we demonstrated that this approach can be extended to nanocomposites growth with increased performances at high magnetic fields using innovative colloidal inks. We confirmed TLAG Coated Conductors technology overcoming the anticipated reactivity limitations. The project could prove TLAG growth of reproducible thick nanocomposite coated conductors. The combinatorial approaches developed and in-situ synchrtron x-ray diffraction experiments were essential. Finally, the optimization of the microstructure pinning landscape for TLAG films and nanocomposites together with the achievement of the overdoped state, to increase the condensation energy and therefore reach ultimate performances at high fields, was successfully reached controlling the oxygenation process with O2/O3 mixers at low temperatures. Overall, I am very satistfied with the results from this project, which I expect will help to boost coated conductors to market. The two awarded ERC-PoC (IMPACT and SMS-INKS) will strongly contribute in this direction. ULTRASUPERTAPE has opened a new frame for complex film growth by establishing new processing paths where interfaces boost novel/improved performances deeply influencing the field of functional materials and its applications. Superconducting nanocomposite coated conductor architecture from TLAG growth process
