Abstract: This invention provides a process for the preparation of the precursor used in the fabrication of Y--Ba--Cu--O superconductors. This process mainly uses solgel technology via the nitrate route by using a dicarboxylic acid. Among the dicarboxylic acids, oxalic acid is the best for preparing the precursor which can be fabricated into a good superconductor.

Abstract: A homogenous coprecipitation method by which superconducting oxides having perovskite-like structure, such as YBa2Cu307-x, can be produced in mass, in which urea is used as solvent to adjust and control the PH value of an aqueous nitrate solution. The coprecipitation method of this invention comprises following steps: (a) preparing an aqueous mixture containing Y, Ba and Cu salts with molar ratio of 1:2:3 wherein Y being 0.068M; (b) adding 5-10 moles of oxalic acid per one mole of Y and 20-250 moles of urea per moles of Y into the aqueous mixture; (c) heating the aqueous mixture to a temperature range of 80.degree. to 100.degree. C. to proceed a hydrolysis of the urea such that PH value of the aqueous mixture will be gradually elevated by NH.sub.3 gas evoluted from the urea hydrolysis; and (d) cooling the temperature of the aqueous mixture to room temperature at which time a desired uniform PH value is reached. After cooling, pale blue homogeneous coprecipitates of the superconducting oxides can be obtained.