BISMUTH-BASED SUPERCONDUCTORS PREPARED BY A SOLUTION TECHNIQUE

High-temperature superconductors of the BiSrCaCuO and (Bi, Pb)SrCaCuO 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. © 1990.