Chemical solution deposition (CSD) of YBa2Cu3O7−δ (YBCO) nanocomposites from colloidal precursor solutions containing double metal oxide preformed nanocrystals is a promising, costeffective and reproducible approach to produce superconducting films with high critical current density (Jc) and enhanced pinning. Here, the influence of the preformed nanocrystal composition on the microstructure and superconducting properties of the YBCO nanocomposite films is studied, with a focus on establishing a simple and scalable process to grow nanocomposites that can be transferred to grow nano-added coated conductors. Colloidal stable BaZrO3, BaHfO3, BaTiO3 and SrZrO3 nanocrystals (3-6 nm in diameter) were synthesized and added to an environment-friendly low-fluorine YBCO precursor solution. High-quality superconducting layers were grown on LaAlO3 single-crystal substrates from these four nanocomposite precursor solutions in a single deposition process, without the need of a seed layer, yielding Jc of 4-5 MA/cm² at 77 K in self-field. The different YBCO microstructures produced by the four types of nanocrystals and the resulting microstrain of the films are compared and related with the magnetic-field and angular dependence of Jc. We demonstrate the BaHfO3-containing nanocomposite as the best-performing with a homogeneous distribution of nanoparticles with 7 nm in average diameter and a high density of stacking faults, which leads to some of the best superconducting properties ever achieved via low-fluorine CSD. The Jc exhibits a much smoother decay in applied magnetic fields and a much more isotropic behaviour for non-parallel magnetic fields, and the pinning force is increased by a factor of 3.5 at 77 K and 1 T with respect to the pristine film.

To reduce the fabrication costs while maximizing the superconducting and pinning properties of YBa2Cu3O7−δ (YBCO) nanocomposite films, the drop-on-demand ink-jet printing technique was used to deposit colloidal YBCO inks onto LaAlO3 substrates. These inks containing preformed HfO2 nanocrystals were carefully adjusted, prior to the jettability, as the droplet formation depends on the rheological properties of the inks themselves. After carefully adjusting printing parameters, 450-nm thick pristine YBCO films with a self-field critical current density (Jc) of 2.7 MA cm−² at 77 K and 500-nm thick HfO2-YBCO nanocomposite films with a self-field Jc of 3.1 MA·cm−² at 77 K were achieved. The final HfO2-YBCO nanocomposite films contained dispersed BaHfO3 particles in a YBCO matrix due to the Ba2+ reactivity with the HfO2 nanocrystals. These nanocomposite films presented a more gradual decrease of Jc with the increased magnetic field. These nanocomposite films also showed higher pinning force densities than the pristine films. This pinning enhancement was related to the favorable size and distribution of the BaHfO3 particles in the YBCO matrix.

This manuscript introduces and experimentally demonstrates a novel concept of selective metal ion irradiation by combining bipolar HIPIMS with conventional DC magnetron sputtering operation and simple DC biasing. The addition of the positive pulse to a conventional HIPIMS discharge accelerates the predominantly metal ions created during the negative HIPIMS phase with an energy proportional to the positive pulse amplitude and ionization state. Two distinct metal elements with large difference in atomic mass (Cr and Nb) are used on this work to irradiate a TiAlN matrix which is being deposited by conventional DCMS. The positive acceleration voltages used for both Cr and Nb discharges were varied between 0 to +200 V to analyze the influence of Nb and Cr metal ion irradiation on the mechanical and microstructural properties of TiAlN films. Even though the total metal ion incorporation into the TiAlN matrix for both Cr and Nb is less than 10% at%, strong effects are observed on the resulting film properties. It was observed that use of the lighter metal ion Cr is more beneficial than the heavier metal ion Nb. The Cr bombardment allows a hardness improvement from 7 to 22 GPa as well as a reduced film accumulated stress at the highest positive acceleration voltage. From the XRD measurements it is observed that the Cr atoms are inserted into the TiAlN cubic matrix maintaining its crystalline structure. However, the bombardment with the high-mass metal ion (Nb) promotes the deformation of the cubic TiAlN matrix, resulting in a spinodal decomposition and further degradation of the crystalline structure with the appearance of the hexagonal wurtzite-type Al-rich phase. This is also translated to the resulting film mechanical properties, as hardness rapidly decreases from 25 to 10 GPa and stress increases linearly with the positive voltage acceleration.

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.