Importance of the pyrolysis for microstructure and superconducting properties of CSD-grown GdBa2Cu3O7−x-HfO2 nanocomposite films by the ex-situ approach

Abstract

For the first time, GdBa2Cu3O7−x nanocomposites were prepared by chemical solution deposition following the ex-situ approach. In particular, ~ 220 nm GdBa2Cu3O7−x-HfO2 (GdBCO-HfO2) nanocomposite films were fabricated starting from a colloidal solution of 5 mol% HfO2 nanoparticles. Hereby, one of the main challenges is to avoid the accumulation of the nanoparticles at the substrate interface during the pyrolysis, which would later prevent the epitaxial nucleation of the GdBCO grains. Therefore, the effect of pyrolysis processing parameters such as heating ramp and temperature on the homogeneity of the nanoparticle distribution has been investigated. By increasing the heating ramp to 300 °C/h and decreasing the final temperature to 300 °C, a more homogenous nanoparticle distribution was achieved. This translates into improved superconducting properties of the grown films reaching critical temperatures (Tc) of 94.5 K and self-field critical current densities ($${J}_{\mathrm{c}}^{\mathrm{sf}}$$ J c sf ) at 77 K of 2.1 MA/cm2 with respect to films pyrolyzed at higher temperatures or lower heating ramps.

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

“…Previous analyses of films during the pyrolysis were mainly performed using ex-situ measurements and mainly on thin films (∼200-300 nm) [20,59,[131][132][133], however, these exsitu approaches limit the information about the kinetic aspects of the complex pyrolysis. To go beyond this restrained picture, an investigation combining different experimental tools, most of them working under in-situ conditions, was performed using annealing conditions close to those used in the pyrolysis process.…”

“…The thorough knowledge generated about the physicochemical transformations occurring during the pyrolysis process has become very useful to maximize the film thickness [139], as well as to accelerate the pyrolysis step [59,133]. This was demonstrated in an effort to define the best parameters for thick (∼1 µm) film deposition of YBCO films by single deposition IJP to approach the thickest CSD films reached by slot die coating or spin coating by multideposition [29,126,140].…”

“…Another route to minimize accumulation of NPs at the surface was shown to be associated to the pyrolysis process, i.e. when the heating ramp is increased the density of NPs at the substrate interface decreased and so the superconducting properties were improved [133]. In all these cases coarsening is in any case still quite relevant and the final NP size of the trapped BZO NPs lies in the range of ∼12-25 nm for an initial ZrO 2 particle size of ∼7 nm [96].…”

An Evaluation of Nanoparticle Distribution in Solution-Derived YBa2Cu3O7−δ Nanocomposite Thin Films by XPS Depth Profiling in Combination with TEM Analysis

“…In addition to being applicable to a wide range of elements or combinations of elements and/or materials, including metals, ceramics and polymers, XPS provides quantitative and chemical bonding information, although one needs to be aware of preferential sputtering and reduction by X-rays. Previous work already demonstrated the use of XPS depth profiling in the analysis of ZrO 2 added YBCO [5] and HfO 2 -added GdBa 2 Cu 3 O 7−δ [27] nanocomposite films. Recently, Santoni et al [28] showed that the Zr/Y ratio is a reliable parameter to evaluate zirconium distribution in YBCO matrix.…”

Transport measurements in single-grain GdBCO+Ag bulk superconductors processed by infiltration growth

“…Fig 6. Temperature dependence of electrical resistance R measured for the IG-processed GdBCO+Ag prepared specimen (a, inset) in the absence of an applied magnetic field and (a) under different magnetic fields in the range 1-9 T (B||c-axis, step size 1 T) and 0.5 T. The irreversibility line (IRL) of the sample (black circles and dashed line) in (b) is compared to a similar curve for a standard, pristine GdBCO film (red circles and red dashed line)[18,19]. The dashed lines are a fit of the data to expression(1) …”