Analytical electron microscopy study of the composition of BaHfO3_3; nanoparticles in REBCO films: the influence of rare-earth ionic radii and REBCO composition

The critical current density of superconducting rare-earth barium copper oxide (REBCO) thin films is enhanced by adding nanoparticles to generate artificial pinning centers. Barium-based perovskites are popular nanoparticle materials. Although typically considered chemically unreactive in the surrounding REBCO matrix, previous studies have shown experimental evidence for rare-earth element (REE) incorporation from REBCO into the nanoparticles. However, not much is currently known about this chemical interaction

Importance of the pyrolysis for microstructure and superconducting properties of CSD-grown GdBa2_{2}Cu3_{3}O7−x_{7-x}-HfO2_{2} nanocomposite films by the ex-situ approach

For the first time, GdBa$_{2}$Cu$_{3}$O$_{7-x}$ nanocomposites were prepared by chemical solution deposition following the ex-situ approach. In particular, ~ 220 nm GdBa$_{2}$Cu$_{3}$O$_{7-x}$-HfO$_{2}$ (GdBCO-HfO$_{2}$) 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 (T$_{c}$) of 94.5 K and self-field critical current densities ($_{c}$$^{sf}$) at 77 K of 2.1 MA/cm$^{2}$ with respect to films pyrolyzed at higher temperatures or lower heating ramps

CSD-grown Y1−xGdxBa2Cu3O7−δ-BaHfO3 nanocomposite films on Ni5W and IBAD technical substrates

Chemical solution deposition (CSD) was used to grow Y1-xGdxBa2Cu3O7-delta-BaHfO3 (YGBCO-BHO) nanocomposite films containing 12 mol% BHO nanoparticles and various amounts of Gd, x, on two kinds of buffered metallic tapes: Ni5W and IBAD. The influence of the rare-earth stoichiometry on structure, morphology and superconducting properties of these films was studied. The growth process was carefully studied in order to find the most appropriate growth conditions for each composition and substrate. This led to a clear improvement in film quality, probably due to the reduction of BaCeO3 formation. In general, the superconducting properties of the films on Ni5W are significantly better. For x > 0.5, epitaxial 270 nm thick YGBCO-BHO films with T-c > 93 K and self-field J(c) at 77 K 2 MA/cm(2) were obtained on Ni5W. These results highlight the potential of this approach for the fabrication of high-quality coated conductors

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

For the first time, GdBa2Cu3O7-x nanocomposites were prepared by chemical solution deposition following the ex-situ approach. In particular, similar to 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 degrees C/h and decreasing the final temperature to 300 degrees C, a more homogenous nanoparticle distribution was achieved. This translates into improved superconducting properties of the grown films reaching critical temperatures (T-c) of 94.5 K and self-field critical current densities (J(c)(sf)) at 77 K of 2.1 MA/cm(2) with respect to films pyrolyzed at higher temperatures or lower heating ramps