Synthesis of Bi-based superconducting powders through the freeze drying

High-purity submicron Bi–Pb–Sr–Ca–Cu–O particles were prepared by the freeze-drying method from modified aqueous solutions of the corresponding metal nitrates. Synthesis through an aerosol enables the generation of ultrafine multicomponent powders with improved compositional homogeneity. Bi–Pb–Sr–Ca–Cu–O rich particles obtained through freeze drying are characterized with the mean particle size below 1 μm, irregular shape, smooth surface and they are slightly agglomerated. The BET surface area is 2.5 m2 g−1 and the mean crystallite size is calculated to be 231 nm. High reactivity of the particles and appearance of the liquid phase produce increased crystallinity, interparticle sintering and hard agglomerate formation during additional heat treatment in oxygen.