Influences of Y2O3 nanoparticle additions on the microstructure and superconductivity of YBCO films derived from low-fluorine solution

Low-fluorine YBCO precursor solutions with metallic ion molar ratio of Y3+:Ba2+:Cu2+ = (1 + λ):2:3 (λ = 0, 0.05, 0.1, 0.15, 0.2, 0.3) were prepared using fluorine-free yttrium acetate, copper acetate and fluorinated Ba-TFA as starting materials. Using the yttrium-excess YBCO solutions, YBCO–Y2O3 nanocomposite films were prepared on (0 0 1)-oriented LaAlO3 single-crystal substrates by dip-coating process. The growth orientation and microstructure of the as-prepared YBCO–Y2O3 nanocomposite films were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Both the electrical transport and magnetization methods were used to measure the superconducting performance of the films. The results show that Y2O3 nanoparticles with the diameter of 5–6 nm are formed and well dispersed in YBCO matrix. These nanoscaled Y2O3 nanoparticles and the induced nano-sized crystal defects can act as the flux pinning centers, thus leading to the improvement of critical current density Jc of YBCO films at all magnetic field orientations.