Low-Fluorine Ba-Deficient Solutions for High-Performance Superconducting YBCO Films

Abstract

High-performing superconducting YBa2Cu3O7–x (YBCO) films are fabricated by a chemical solution deposition methodology through novel barium-deficient low-fluorine solutions. The precursor solutions, distinguished for being straightforward, inexpensive and eco-friendly, allow us to reduce the growing temperature of YBCO down to 750 °C. We investigated the influence of the growing temperatures on both the microstructure and superconducting properties of YBCO films by using conventional thermal annealing and flash-heating approaches. A clear correlation between the growing temperature (Tg) and the superconducting performance of the films was obtained with improved performances observed at low Tg.

Influence of growth temperature on the pinning landscape of YBa2Cu3O7− δ films grown from Ba-deficient solutions

“…Low-fluorine Ba-deficient precursor solutions were prepared by dissolving barium, copper acetates, and yttrium TFA with a ratio of Y:Ba:Cu equal to 1:1.5:3 in a mixture of organic solvents consisting of propionic acid (30%) and methanol while heating at 30 • C [8]. Precursor solution was deposited by spin coating with an angular velocity of 6000 rpm, angular acceleration of 6000 rpm s −1 and spinning duration time of 2 min on 5 × 5 mm 2 (100) LaAlO 3 single-crystal substrates.…”

“…So, growth temperature can be used to naturally tune the defect pinning landscape of YBCO films without the need to incorporate additional secondary phases. We demonstrated in [8] that by using an optimal growth temperature of 750 • C, which gave a good compromise between percolation (good texture) and pinning performance, we can obtain very high self-field critical current values, 60 MA cm −2 and 7 MA cm −2 , at 5 K and 77 K, respectively. Moreover, we observed that samples grown at lower temperatures showed smoother J c (H) dependencies evidencing a higher density of defects in the YBCO matrix.…”

“…Among the different parameters that may be changed to optimize the performance of CSD films, one can play with the stoichiometry of the starting solution. In this sense, Ba-deficient compositions have shown improved performances with extremely high critical current density values [8][9][10]. In a recent publication, we observed that by using lowfluorine Ba-deficient solutions, YBCO c-axis nucleation can be obtained at much lower temperatures (T ∼ 730 • C) than those needed in stoichiometric films, thus significantly extending the epitaxial temperature growth window [8].…”

“…In this sense, Ba-deficient compositions have shown improved performances with extremely high critical current density values [8][9][10]. In a recent publication, we observed that by using lowfluorine Ba-deficient solutions, YBCO c-axis nucleation can be obtained at much lower temperatures (T ∼ 730 • C) than those needed in stoichiometric films, thus significantly extending the epitaxial temperature growth window [8]. The growth temperature plays an important role on the amount and nature of the pinning defects induced within the YBCO matrix, and the associated pinning anisotropy and strength [11,12].…”

Unravelling the Crystallization Process in Solution-Derived YBa2Cu3O7-δ Nanocomposite Films with Preformed ZrO2 Nanocrystals via Definitive Screening Design

“…In our case, in order to improve the properties of the films, the first requirement is to design a suitable growth process that allows obtaining epitaxial, c -axis oriented films. There are different strategies to improve the growth process to achieve that process: (1) adding silver to stabilize the c -axis nuclei, (2) adjusting the stoichiometric ratio of Y:Ba:Cu in the YBCO precursor solution, , (3) introducing a pristine YBCO seed layer to ensure c -axis growth of the YBCO nanocomposite, and (4) modifying the crystallization process. Applying DSD for these four points, we achieved YBCO nanocomposite films with larger amounts of ZrO 2 nanocrystal than had been possible before (up to 12.5 mol %) without damaging yet even improving the YBCO microstructure and the superconducting properties of the films.…”