Coprecipitation-based micro-reactor process to synthesize soft-agglomerated ultrafine BiPbSrCaCuO powder with low carbon content

A new process, termed coprecipitation-based micro-reactor process (CMP), has been developed to synthesize highly homogeneous ultrafine BiPbSrCaCuO superconductor precursor powder with soft agglomerate and low carbon content. The new process includes three main steps: (1) the ultrafine precipitates with specific composition are prepared by oxalate coprecipitation in a mixed liquid medium with low surface tension; (2) the precipitates are in situ dispersed in the medium; (3) the as-prepared colloidal solution is quickly subjected to heat treatment to get soft-agglomerated BiPbSrCaCuO powder with ultrafine particles (∼ 0.3 μm), low carbon content (< 200 ppm) and typical main phase compositions of (Bi,Pb)₂Sr₂CaCu₂O_x, CaPbO₄, CuO, Ca₂CuO₃, Bi₂Sr₂CuO_x. The typical characteristics of CMP are such that each precipitate particle behaves like a micro-reactor during heat treatment, which leads to the minimization of the probabilities of contact, agglomerate or sintering between particles as compared to the traditional coprecipitation process. The CMP powder can be sintered into highly pure (Bi,Pb)₂Sr₂Ca₂Cu₃O_x superconductor in short time.