Size-controlled spontaneously segregated Ba2YTaO6 nanoparticles in YBa2Cu3O7 nanocomposites obtained by chemical solution deposition

Abstract

We present a thorough study of the nucleation and growth processes of the solution-based YBa2Cu3O7–Ba2YTaO6 (YBCO–BYTO) system, carried out with a view to controlling the characteristics of the BYTO phase to meet the requirements for specific power applications. Scanning transmission electron microscopy and x-ray diffraction have been used to characterize the BYTO nucleation and phase evolution during the YBCO–BYTO conversion. At high BYTO loads (>10 mol%), the nanoparticles tend to aggregate, resulting in much less efficiency for generating nanostrained areas in the YBCO matrix, and enhancement of the vortex pinning. Our experiments show that by modifying the nucleation kinetics and thermodynamics of the BYTO, the nucleation mode (homogeneous versus heterogeneous), the particle size and the particle orientation can be controlled. We demonstrate that YBCO–BYTO nanocomposites with high concentration of nanoparticles can be prepared in such a way as to obtain small and randomly oriented nanoparticles (i.e. high incoherent interface), generating highly strained nanoareas in the YBCO, with enhancement in the vortex pinning. We have also observed that the incoherent interface is not the only parameter controlling the nanostrain. The Cu–O intergrowth characteristics must also be a key factor for controlling the nanostrain in future tuning of YBCO vortex pinning.