Modified coprecipitation process of synthesizing Bi-system superconductor precursor powder and its stoichiometry

A modified coprecipitation process is presented based on the stoichiometry study of oxalate coprecipitation process in water medium to synthesize Bi-Pb-Sr-Ca-Cu-O multi-component powder. Its characteristic is that the coprecipitation reaction takes place in a mixed solution medium composed of water and a kind of organic solvent (volume percentage >90%). Thus, it overcomes the serious shortcoming of inability to maintain stoichiometry in Bi-system superconductor powder synthesized by water-medium coprecipitation. The effects of pH value, oxalic acid concentration and aging time on stoichiometry maintenance in precipitate are systematically studied. Bulk material made from the powder prepared by the new modified coprecipitation also shows the success of the new process.