Superconducting YBa₂Cu₃O_7–δ Nanocomposites Using Preformed ZrO₂ Nanocrystals: Growth Mechanisms and Vortex Pinning Properties

Abstract

Although high temperature superconductors are promising for power applications, the production of low‐cost coated conductors with high current densities—at high magnetic fields—remains challenging. A superior superconducting YBa2Cu3O7–δ nanocomposite is fabricated via chemical solution deposition (CSD) using preformed nanocrystals (NCs). Preformed, colloidally stable ZrO2 NCs are added to the trifluoroacetic acid based precursor solution and the NCs' stability is confirmed up to 50 mol% for at least 2.5 months. These NCs tend to disrupt the epitaxial growth of YBa2Cu3O7–δ, unless a thin seed layer is applied. A 10 mol% ZrO2 NC addition proved to be optimal, yielding a critical current density JC of 5 MA cm−2 at 77 K in self‐field. Importantly, this new approach results in a smaller magnetic field decay of JC(H//c) for the nanocomposite compared to a pristine film. Furthermore, microstructural analysis of the YBa2Cu3O7–δ nanocomposite films reveals that different strain generation mechanisms may occur compared to the spontaneous segregation approach. Yet, the generated nanostrain in the YBa2Cu3O7–δ nanocomposite results in an improvement of the superconducting properties similar to the spontaneous segregation approach. This new approach, using preformed NCs in CSD coatings, can be of great potential for high magnetic field applications.

Optimizing Nanocomposites through Nanocrystal Surface Chemistry: Superconducting YBa2Cu3O7 Thin Films via Low-Fluorine Metal Organic Deposition and Preformed Metal Oxide Nanocrystals

“…We infer that the slow growth rate is symptomatic for poor epitaxial growth, resulting in the lower critical current density. Indeed, the fast decomposition of citric acid can interfere with the drying and/or sintering process of the gel as described by Zalamova et al 40 In this regard, it is also worth noting that amino acid capped ZrO2 nanocrystals 25 settle on the LaAlO3 interface during pyrolysis of the YBCO trifluoroacetate precursor, resulting in a disturbed epitaxial growth of YBCO. To investigate whether the same mechanism occurs here, X-ray photoelectron spectroscopy measurements were performed on the pyrolyzed films.…”

“…decanoic acid). 24,25 These types of ligands are of same length scale as the short carboxylic acids (citric and tartaric acid) in this work. From thermogravimetric analysis (TGA, Figure S8 in SI and Table 1), we conclude that the short carboxylates decompose at lower temperatures (250 °C for citric acid and 265 °C for tartaric acid) compared to the copolymer which decomposed around 340 °C.…”

“…To reproducibly gain control over the final microstructural properties of the nanocomposite thin films, we opted to synthesize colloidally stable nanocrystals in advance and add them to the YBCO precursor solution ( Figure 1, stage I). Up to now, only a few attempts have been made at nanocomposites using preformed nanocrystals (Au, CeO2 and ZrO2) [23][24][25] and the success has been limited because the nanocrystals are either pushed to the YBCO surface or accumulated at the substrate interface. The latter hampers the epitaxial growth of YBCO, leading to poor superconducting properties.…”

Influence of Ba2+ consumption and intermediate dwelling during processing of YBa2Cu3O7 nanocomposite films

“…Currently, some research has already investigated on the link between the influence of preformed nanocrystals and its surface chemistry with the final YBCO properties. It has been discovered that preformed nanocrystals can lead to better pinning properties while a choice of ligands is very crucial to obtain good YBCO properties . Nevertheless, understanding of nucleation and growth mechanism of undoped and nanodoped YBCO films during the CSD process of TFA‐MOD methods should be essential to improve the superconducting properties.…”

“…While pulsed laser deposition is already an advanced research method to elucidate the effects of nano‐sized secondary phases on the pinning landscape in high‐temperature superconducting films, there is limited knowledge of the control over the formation of nano‐sized secondary phases during nucleation and growth step of CSD‐YBCO methods. In previous research, it was seen that the addition of single metal oxide nanocrystals (eg, ZrO 2 ) leads to the formation of double metal oxide nanocrystals (eg, BaZrO 3 ) due to its Ba 2+ consumption. This latter has a negative effect on the formation of (002)‐oriented BaF 2 superstructure, which acts as good template for nucleation and growth of YBCO nanocomposite film.…”