Improvement of multiple oxide properties: effect of gel processes on the quality of Bi2Sr2CaCu2O8 + δ superconducting powders

Abstract

Different gel processes were devised to synthesize Bi₂Sr₂CaCu₂O_8+δ (Bi2212)powders by sol–gel method. The phase purity, grain size and crystallinity of Bi2212 powders were dramatically improved by a modified sol–gel method called Pechini. Meanwhile, the sintering time was correspondingly reduced by a half. According to the investigations of different gel mechanism on the quality of Bi2212 powders, the polymerization increased the stability of gel network which inhibited some complexes segregated from gel network before auto-combustion. Furthermore, the esterification reduced the amount of free metal ions and improved the homogeneity of gel.