Solution design for low-fluorine trifluoroacetate route to YBa₂Cu₃O₇films

Abstract

In the context of CSD-MOD growth of coated conductors for low cost and scalable production of YBCO coated conductors, new solutions are proposed in accordance with the new requirements concerning environmental safety and product performance. Looking at these objectives we will present here our work in the preparation of metallorganic precursor solutions with reduced fluorine content, which fulfill the requirements of superconducting YBCO epitaxial layers, leading to high superconducting performance. Solutions with low fluorine precursors with different solvents and amounts of additives have been stabilized and their rheology modified for substrate wettability. Thermal decomposition analysis and infrared spectroscopy performed directly in films, have revealed the different decomposition steps and NMR analysis could unveil the chemical reactions taking place in the solution. Upon optimization of the growth process parameters, T c and J c (77K) of 90 K and 3-4 MA/cm 2 are obtained.

Thermal decomposition of yttrium propionate: film and powder

“…Conversely, although the XRD pattern of the present work is similar to [19], there are significant differences between our FTIR and XRD pattern and those reported in the literature [16][17][18][19], also there are significant differences among the different structures reported in the literature. Indeed, in carboxylates, the carboxylate bond and the crystalline structure depend strongly on the presence of crystallization water [2,[26][27][28], so that the distance between the asymmetric and symmetric carboxylic bands [Δν= ν as (COO…”

“…Since in the presence of oxygen degradative oxidation is likely to take place, for films in a dry O 2 atmosphere decomposition can be triggered by the oxidation of the propionate groups to acetaldehyde, CO 2 and propionic acid to produce the reaction scheme shown in β (Hydrolysis + oxidation) of Fig. 1.…”

“…The relatively recent interest in yttrium propionate (Y-Prop 3 ) has been boosted by its application in the synthesis of YBa 2 Cu 3 O 7-x (YBCO) [1][2][3]. YBCO belongs to the second generation of high-temperature superconductors, which are applied in the form of tapes (also called coated conductors, CCs), and thus its entire synthetic process is based on thin film technology.…”

“…In this regard, up to now, there is a wide understanding of the trifluoroacetate (TFA) route [5][6][7] to YBCO, where the precursor solution consists of the trifluoroacetate salts of each metal. However, a major drawback of this route is that the decomposition of the intermediate BaF 2 involves the release of Hydrofluoric acid (HF). It has been stated that out-diffusion of HF is the limiting step in obtaining YBCO during the growth stage [6][7][8][9].…”

“…Indeed, the slow HF diffusion is the main challenge in obtaining cost-competitive YBCO tapes. Therefore, other precursor solutions have been considered, such as low-fluorine [2] or fluorine-free (FF) solutions [10]. In fact, it has been shown that, from FF solutions, YBCO can grow through a liquid-solid reaction [11,12], and this in turn can lead to very high growth rates.…”