Superconducting HfO2-YBa2Cu3O7−δ Nanocomposite Films Deposited Using Ink-Jet Printing of Colloidal Solutions

Progress in the Study of Vortex Pinning Centers in High-Temperature Superconducting Films

Since the discovery of high-temperature superconductors (HTSs), significant progress in the fabrication of HTS films has been achieved. In this review, we intend to provide an overview of recent progress in how and why superconductivity can be enhanced by introducing nanoscale vortex pinning centers. The comprehensive control of morphology, dimension, orientation and concentration of artificial pinning centers (APCs) and the principle of vortex pinning are the focus of this review. According to the existing literature, HTSs with the best superconductivity can be obtained when one-dimensional (1D) and three-dimensional (3D) nanoscale APCs are combined for vortex pinning.

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

This work discusses the development of an analysis routine for evaluating the nanoparticle distribution in nanocomposite thin films. YBa2Cu3O7−δ (YBCO) nanocomposite films were synthesized via a chemical solution deposition approach starting from colloidal YBCO solutions with preformed nanoparticles. The distribution of the nanoparticles and interlayer diffusion are evaluated with X-ray photoelectron spectroscopy (XPS) depth profiling and compared with cross-sectional transmission electron microscopy (TEM) images. It is shown that the combination of both techniques deliver valuable information on the film properties as nanoparticle distribution, film thickness and interlayer diffusion.

Unravelling the Crystallization Process in Solution-Derived YBa2Cu3O7-δ Nanocomposite Films with Preformed ZrO2 Nanocrystals via Definitive Screening Design

A low-cost chemical solution deposition technique was employed to prepare YBa₂Cu₃O_7-δ (YBCO) nanocomposite films starting from a colloidal solution containing preformed ZrO₂ nanocrystals. As previous publications revealed, an increase in the amount of nanocrystals results in a progressive deterioration of the film properties. The parameters that control this process and their interplay are still unknown in detail. Using definitive screening design (DSD), a design-of-experiments approach, allowed determining which of the multiple growth parameters play a key role for improving the superconducting properties of YBCO nanocomposite films even with a large concentration of nanocrystals. In order to show the potential of DSD, it has been applied for the optimization of two different properties: the critical temperature T_c and the full width at half-maximum of the (005) YBCO reflection. This work shows that DSD is a powerful and efficient method that allows optimizing certain processes with a minimal number of experiments.

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, ~ 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 ([Formula: see text]) at 77 K of 2.1 MA/cm2 with respect to films pyrolyzed at higher temperatures or lower heating ramps.