Preparation of YBa₂Cu₃O_7-x (YBCO) Superconductive Film Using Sol-Gel Method

Using alkoxides of Y and Ba and Cu-acetate as raw materials, Y Ba₂Cu₃O_7-x (YBCO) superconductive films were produced through the sol-gel method. When the nonaqueous mixed solution was hydrolyzed under an appropriate condition, a pure and homogeneous YBCO powder could be prepared. Controlling the metal concentration and the temperature of the sol, precursor(gel) films were formed on YSZ substrate by dip-coating. And heating the films in the range of 200°-950°C, changes of the films morphologies, the generated phases and the film reactions with the substrates were studied using scanning electron microscopy and X-ray diffraction. It has been known that to improve the superconductivity of the film it is necessary to sinter it at as high as 950°C and increase its thickness over about 3 µm after sintering. A superconductive film with T_c.off=75 K was obtained by adopting these conditions.