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

Abstract

SmBa2Cu3O7-δ (SmBCO) films have been prepared by chemical solution deposition starting from extremely-low-fluorine solutions (7% fluorine with respect to standard full trifluoroacetate solutions). Smooth and homogeneous SmBCO films could be achieved at heating rates of up to 20 °C/min during pyrolysis. The best films were achieved at a crystallization temperature of 810 °C and 50 ppm of oxygen partial pressure. At these conditions, the ~270 nm thick SmBCO films grow mostly c-axis-oriented with J c sf values at 77 K of ~2 MA/cm2 and critical temperatures Tc of up to 95.0 K. These results demonstrate that using extremely-low-fluorine solutions is very attractive since the production rate can be largely increased due to the solutions’ robustness during pyrolysis retaining a remarkable quality of the grown films. Nevertheless, further optimization of the growth process is needed to improve the superconducting properties of the films.

RE BCO mixtures with large difference in rare-earth ion size: superconducting properties of chemical solution deposition-grown Yb 1− x Sm x Ba 2 Cu 3 O 7− δ films

“…The YbSmBCO-ELF solutions were prepared following the procedure explained in detail in [12]: Yb, Sm and Cu acetates ( purity > 99.99%, Alfa Aesar) were dissolved in the desired stoichiometry in propionic acid (99%). Concerning Ba, 1/3 of the Ba acetate was dissolved in trifluoroacetic acid and deionized water to convert it to TFA while the remaining 2/3 were also dissolved in propionic acid together with the other acetates.…”

“…The final solutions with different Yb/Sm compositions were deposited on (100)-oriented LaAlO 3 (LAO) single crystal substrates via spin coating (6000 r.p.m., 2 min). The as-deposited films were pyrolysed and grown with the thermal profiles and gas mixture given in [12]: heating with 20°C min −1 in a flow of 2 l min −1 of pure O 2 for the pyrolysis at 500°C, and heating with 20°C min −1 in 2 l min −1 of an N 2 /O 2 mixture with 50-200 ppm O 2 for the growth at 720-820°C. The pyrolysis parameters were the same for all solutions while crystallization temperature, T crys , and oxygen partial pressure, pO 2 , had to be adjusted in the given ranges for each composition.…”

“…In particular, the syntheses of SmBCO and YbBCO films are probably two of the most challenging ones among the REBCO phases because the ion size of both compounds are almost at the superior and inferior ends of the line of possible lanthanide candidates. Recently, our group has been able to prepare SmBCO films by chemical route showing the difficulties associated with the tendency of Sm 3+ ions to occupy the Ba 2+ sites [12]. Also, several works reported the problems in preparing YbBCO films, leading, in general, to quite modest maximum critical temperatures T c ∼ 90 K and self-field critical current densities, J c sf , at 77 K of approximately 1 MA cm −2 [13][14][15][16][17][18].…”

Pyrolysis study of solution-derived superconducting YBa2Cu3O7films: disentangling the physico-chemical transformations

“…[10][11][12][13]28,31,32 Moreover, the use of low-fluorine solutions for YBCO film growth, beyond the benefit for the environment, possess a reduced hygroscopic behavior, which contributes to achieve improved film quality during pyrolysis [33][34][35] or may also allow to perform faster pyrolysis processes. 36 It is therefore an important issue to carry out a detailed investigation of the decomposition mechanisms and their influence on the microstructure of YBCO films based on these solutions.…”

Development of a Fluorine-Free Polymer-Assisted-Deposition Route for YBa2Cu3O7−x Superconducting Films

“…However, one of the major drawbacks of this method is the liberation of toxic HF during the YBCO pyrolysis/crystallization steps [5]. Continuous efforts are being carried out in the development of low-fluorine (see for example [6,7]) and fluorine-free chemical solution deposition processes [8][9][10][11][12]. These approaches consist of dissolving carboxylates, such as acetates, propionates, etc., or β-diketonates, as metal precursors in a common solvent, usually organic acids, and combining the solutions to yield the desired stoichiometry.…”