Y1Ba2Cu3Ox films of about 50-60 mu m thickness on Ni substrates were fabricated by spraying a suspension consisting of YBCO powders. The films which were fired under flowing argon and then annealed in oxygen showed relatively high J(c) values of about 500 A/cm(2) (77 K, 0T) over a firing temperature range from 910-950 degrees C. When the films were fired at 960 degrees C, the Ni whose concentration was about 4 at.% and large-size cracks were found to be present on the surface of the film, resulting in the destruction of the superconducting properties of the film. The reaction products produced near the interface regions and on the surface of the films were also studied.