Preparation of YBCO Superconducting Nano-Composite Films by MOCVD

Y-Ba-Cu-0 (YBCO) superconducting films were prepared on SrTiO₃(100) substrates by metalorganic chemical vapor deposition. The precursors used were β-diketone chelates of Y, Ba and Cu. The YBCO films, having superconducting transition temperature defined by zero resistivity (T_c(R=0)) above 90 K and critical current density (J_c) over 10⁶ A/cm² at 77 K and 0 T, were obtained at the conditions of oxygen partial pressure (Poj) and deposition temperature (T^dep) near the CuO-Cu₂O-O₂equilibrium line (PO₂=3.6 Torr-T_dep= 850°0 and PO₂=0.036 Torr - T_dep=700-720°C). The films prepared at these conditions showed J_c over 10⁴ A/cm² at 77 K in high magnetic fields above 20 T. The nano-composite structure of the YBCO films was studied by transmission electron microscopy. CuO and Y₂Cu₂0₅ grains with a size of 0.1-2 µm were included. The precipitates of about 10 nm in size were observed in the matrix of the YBCO films.