A low-fluorine solution with a 2:1 F/Ba mole ratio for the fabrication of YBCO films

Abstract

In the reported low-fluorine MOD-YBCO studies, the lowest F/Ba mole ratio of the precursor solution was 4.5. However, further lowering the F/Ba ratio is important according to the researches of YBCO thick film. On the other hand, the F/Ba ratio is necessary to be at least 2 for the full conversion of the Ba precursor to BaF2 to avoid the formation of BaCO3, which is detrimental to the superconducting performance. In this study, a novel solution with the F/Ba mole ratio of 2 was developed, in which the fluorine content was only about 10.3% of that used in the conventional TFA-MOD method. Attenuated total reflectance-Fourier transformed-infrared spectra(ATR-FT-IR) revealed that BaCO3 was remarkably suppressed in the as-pyrolyzed film and eliminated at 700 • C. Thus YBCO films with a critical current density (Jc) over 5 MA cm −2 (77 K, 0 T, 200 nm thickness) could be obtained on LAO single crystal substrates. In-situ FT-IR spectra showed that no obvious fluorinated gaseous by-products were detected in the pyrolysis step, which indicated that all of the F atoms might remain in the film as fluorides. X-ray diffraction (XRD) θ/2θ scan showed that BaF2, but neither YF3 nor CuF2, was detected in the films quenched at 400 -800 • C. The formation priority of BaF2 over YF3 and CuF2 was interpreted by the chemical equilibrium of the potential reactions. Our study could enlarge the synthesis window of the precursor solution for MOD-YBCO fabrication and open a gate to study the fluorine content in the precursor solution continuously and systematically.

Rapid Pyrolysis of SmBa2Cu3O7-δ Films in CSD-MOD Using Extremely-Low-Fluorine Solutions

“…However, the reduction of the fluorine content in the precursor solution has other advantages, too: It is environmentally friendly and can also improve the homogeneity of the films during the pyrolysis process. Using ELF precursor solutions, excellent superconducting properties have been achieved in YBCO films with much faster heating rates than with other types of solutions [20,22]. However, only little work has been spent to grow REBCO films with other rare earth elements with ELF solutions.As pointed out by Wu et al [20] and Li et al [22], the reaction mechanism for the formation of REBCO films using ELF solutions is still a "BaF 2 " process, which is a well-understood process.…”

High Critical Current Density of YBa2Cu3O7−x Superconducting Films Prepared through a DUV-assisted Solution Deposition Process

“…8(b) shows the R-T curve of the film irradiated for 100 minutes, and the critical transition temperature was approximately 92 K. The J c of UV-irradiated YBCO films increased with irradiation times, since the prolonging of irradiation times promoted the decomposition of organic compounds, enhanced the removal of the carbon residue, and effectively avoided the copper segregation in the precursor films. In terms of YBCO films prepared using conventional pyrolysis method, the best J c values were 5 MA/cm 2  2930, which were still lower than the films UV irradiated for 100 minutes (7.95 MA/cm 2 ). Obviously, the improved density and uniform element distribution in the precursor films were the primary reasons for the enhanced J c of YBCO films.…”

An All Sol-Gel Process for the Heteroepitaxial Growth of YBa2Cu3O7−x/LaNiO3/YBa2Cu3O7−x Tri-layer

“…In terms of practical application, the sol-gel method for the preparation of SNS junctions is promising because of its low cost and scalability. Recently, significant advances have been made in growing both YBCO and textured oxide films using the sol-gel method [9,10]. However, heteroepitaxial growth on YBCO/LaNiO 3 /YBCO tri-layers remains challenging, since a sharp interface between YBCO and LaNiO 3 films is not easy to obtain at a high temperature of approximately 800 • C, which is the typical temperature for the heat treatment of YBCO films in the sol-gel route [9,11].…”