Effect of precursor composition on J_c enhancement of YBCO film prepared by TFA-MOD method

Superconductive YBCO thin films have been prepared by trifluoroacetate (TFA) metalorganic deposition (MOD) method. Non-stoichiometric precursor solutions with cation ratios of Y:Ba:Cu = 1 + x:2:3 (x = 0, 0.05, 0.1, 0.15 and 0.2) have been prepared by dissolving high purity Y₂O₃, BaCO₃ and CuO powders into trifluoroacetate. Coated film was calcined at lower temperature in a moisture-containing oxygen atmosphere. Superconducting YBCO films have been obtained by conducting a conversion heat treatment at higher temperature in a moisture-containing Ar (1000 ppm oxygen) atmosphere. Critical current density (J_c) of YBCO film was increased with the amount of excess yttrium in YBCO film and revealed maximum J_c for x = 0.15 and decreased again for x = 0.2. Four times higher J_c was obtained for the film with x = 0.15 compared to that of the film prepared from stoichiometric solution of Y:Ba:Cu = 1:2:3. It is considered that the densification of microstructure and absence of a-axis grains attributed to the enhancement of J_c in the film made of non-stoichiometric solution.