Chemical Solution Approaches to YBa<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>7−δ</SUB>-Au Nanocomposite Superconducting Thin Films

Abstract

We explore the feasibility of preparing YBa2CU3O7-Au (YBCO-Au) nanocomposite thin films by chemical solution deposition (CSD). Two approaches were used: (i) A standard in-situ methodology where Au metallorganic salts are added into the precursor solution of YBCO trifluoroacetate (TFA) salts and (ii) a novel approach where stable colloidal solutions of preformed gold nanoparticles (5-15 nm) were homogeneously mixed with TFA-YBCO solutions. A detailed analysis of the microstructure of the films showed that in both cases, there is a strong tendency of gold nanoparticles to migrate to the film surface. However the kinetics of this migration evidences important differences and in the case of preformed nanoparticles their size remains unchanged (a few nanometers) whereas for the in-situ nanocomposites gold ripening leads to large particles (hundreds of nanometers). The grown YBCO-Au films showed good superconducting characteristics (J(c) 2 MA/cm2 at 77 K) but the absence of Au inclusions inside the YBCO matrix explains the fact that no enhancement of vortex pinning was observed.

High Critical Current Density and Enhanced Pinning in Superconducting Films of YBa2Cu3O7−δ Nanocomposites with Embedded BaZrO3, BaHfO3, BaTiO3, and SrZrO3 Nanocrystals

“…The rest of the film is strongly textured, with highly coherent twin boundaries and very low concentration of other defects; only a few Y124 planar defects surrounding the large BTO clusters were observed. The aggregation of nanoparticles seen in the BTO-added film, has been observed in previous works using different preformed nanocrystals such as ZrO2, CeO2 or Au[15][16][17][18][19] . The reason why BTO nanocrystals tend…”

“…This offers superior control over size, shape, crystallinity and concentration of the nanocrystals and therefore over the final microstructure of the nanocomposite films. [15][16][17][18][19] However, previous studies have shown that improper choice of nanoparticle composition leads to agglomeration of the preformed nanoparticles during the thermal processing of the layers [18][19] as well as to accumulation of the nanocrystals on the substrate 15 or at the YBCO surface 17 . These effects worsen the superconducting properties and hinder the pinning enhancement.…”

“…7,[23][24] This implies another challenge for the ex situ approach because the colloidal nanocrystal solutions stable in TFA-based precursor solutions (pH = 2) might not be stable in the higher pH of the low-fluorine solution (pH = 6). 19 Moreover, the choice of ligand has been proven to have a dramatic effect on the final properties of the nanocomposite 16,25 . In this work 2-[2-(2-methoxyethoxy)ethoxy]acetic acid [26][27] is used since it can stabilize all the as-synthesized double metal oxide nanocrystals-BaZrO3 (BZO), BaHfO3 (BHO), BaTiO3 (BTO), and SrZrO3 (SZO)-and is completely decomposed after the pyrolysis at 400 °C of the films (see Supporting Information (SI), Figure S1), leaving no organic residues in the layers.…”

Control of nanostructure and pinning properties in solution deposited YBa2Cu3O7−x nanocomposites with preformed perovskite nanoparticles

“…The development of a more versatile route to prepare CSD-based YBCO nanocomposites using already preformed nanoparticles (pn-nanocomposites) has opened many new opportunities to design the nanostructure and pinning properties of YBCO nanocomposites 38–42 . In this case, a colloidal solution of oxide nanoparticles with a well-defined size, shape and concentration is mixed with a precursor solution containing the Y-, Ba- and Cu- metalorganic salts.…”

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

“…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.…”