Structural characterization of multi-coated YBCO films processed by metal-organic deposition method

YBCO films were fabricated using the TFA-MOD process. The effects of film thickness on phase formation, degree of texture, microstructures, and critical properties were evaluated by X-ray diffraction, pole-figure, and transmission electron microscopy. The films were prepared with various thicknesses by producing multi-coated films by repeating the dip-coating and calcining processes. The microstructure and resultant critical current (I_c) and critical current density (J_c) varied remarkably with film thickness: the I_c increased from 39 to 169 A/cm-width, while J_c ranged from 0.85 to 0.92 MA/cm² with increasing number of coatings from one to three or four. Both values decreased when further coatings were applied as a result of microstructural degradation. It is believed that this decrease in I_c for the multi-coated film is partly due to the presence of a second phase, pores, and poor texture formability. The optimum thickness for maximizing both the I_c and J_c values is believed to be in the range of 1.1-1.7 μm.