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

Achieving low cost, safe, reproducible, and high performance superconducting thin films of YBa 2 Cu 3 O 7−δ is essential to bring this material to the energy market. Here, we report on the chemical solution deposition of YBa 2 Cu 3 O 7−δ nanocomposites from environmentally benign precursors with a low fluorine content. Preformed ZrO 2 nanocrystals (3.5 nm) were stabilized in a methanolic precursor solution via two strategies: charge stabilization and steric stabilization. Counterintuitively, charge stabilization did not result in high quality superconducting layers, while the steric stabilization resulted in highly reproducible nanocomposite thin films with a self-field J c of 4–5 MA cm –2 (77 K) and a much smaller decay of J c with magnetic field compared to YBa 2 Cu 3 O 7−δ without nanocrystals. In addition, these nanocomposite films show a strong pinning force enhancement and a reduced J c anisotropy compared to undoped YBa 2 Cu 3 O 7−δ films. Given the relationship between the nanocrystal surface chemistry and final nanocomposite performance, we expect these results to be also relevant for other nanocomposite research.