Chemical and Microstructural Nanoscale Homogeneity in Superconducting YBa₂Cu₃O_7–x Films Derived from Metal-Propionate Fluorine-free Solutions

Abstract

Research involved in developing alternative energy sources has become a necessity to face global warming. In this context, superconductivity is an appealing solution to enhance clean electrical energy provided that lower production costs can be attained. By implementation of chemical solution deposition techniques and high-throughput growth methods, low-cost nanostructured epitaxial cuprate superconductors are timely candidates. Here, we present a versatile and tunable solution method suitable for the preparation of high-performance epitaxial cuprate superconducting films. Disregarding the renowned trifluoroacetate route, we center our focus on the transient liquid-assisted growth (TLAG) that meets the requirement of being a greener chemical process together with ultrafast growth rates beyond 100 nm/s. We developed a facile, fast, and cost-effective method, starting from the synthesis of metal-propionate powders of Y, Ba, and Cu of high purity and high yields, being the precursors of the fluorine-free solutions, which enable the chemical and microstructural nanoscale homogeneity of YBa2Cu3O7–x (YBCO) precursor films. These solutions present endured stability and enable precise tunability of the composition, concentration, porosity, and film thickness. Homogeneous precursor films up to thicknesses of 2.7 μm through eight layer multidepositions are demonstrated, thus establishing the correct basis for epitaxial growth using the fast kinetics of the TLAG process. YBCO films of 500 nm thickness with a critical current density of 2.6 MA/cm2 at 77 K were obtained, showing the correlation of precursor film homogeneity to the final YBCO physical properties.

Progress in superconducting REBa2Cu3O7 (RE = rare earth) coated conductors derived from fluorinated solutions

“…At that time, the general belief was that it would become impossible to grow REBCO CCs at a reasonable temperature because BaCO 3 was stable at to very high temperatures. Recently, this assumption has been reconsidered and fluorine-free metalorganic precursors have shown to be suitable for CSD routes to CCs, even if BaCO 3 is formed as an intermediate compound [41][42][43][44][45][46][47][48][49]. The fluorine-free approach encompasses completely different growth routes with mechanisms which still require further research to be elucidated [43,46].…”

Transient liquid assisted growth of superconducting YBa2Cu3O7−x films based on pulsed laser deposition

“…Recently, a CSD approach using fast and nonequilibrium transient liquids, namely transient liquid assisted growth (TLAG), demonstrated epitaxial growth of REBCO films and nanocomposites with a competitive increase in growth rates in the range of 100-1000 nm s −1 [18,19], Industrialization of TLAG for CCs manufacturing should allow to decrease the cost/performance ratio of REBCO CCs. The key difference between other liquid-based methods and TLAG is that, the latter, is a non-equilibrium method where a transient Ba-Cu-O liquid is formed previous to the REBCO stable phase, out from a metal-oxide/carbonate nanocrystalline (∼5-20 nm) pyrolyzed matrix including CuO, BaCO 3 and RE 2 O 3 [18,20]. RE ions from the RE 2 O 3 nanocrystallites strongly dissolve in the Ba-Cu-O transient liquid thus generating high supersaturation conditions, enabling its fast diffusion through the liquid to the substrate interface.…”