Bismuth-based superconductors prepared by a solution technique

High-temperature superconductors of the BiSrCaCuO and (Bi, Pb)SrCaCuO systems, with several cation stoichiometries, were prepared by dissolution of the corresponding metallic salts in acetic acid followed by coprecipitation in the presence of oxalic acid. Samples were characterized by X-ray diffraction, thermal analysis (differential and thermogravimetric), and scanning electron microscopy. Temperature dependence of electrical resistivity was also measured. Samples with zero electrical resistivity at 80 K were obtained easily and reproducibly by this solution technique. Doping with lead seems to stabilize the 110 K phase, providing samples with an onset superconducting temperature of 120 K and zero electrical resistance at 103 K.