Preparation of ceria-stabilized zirconia microspheres by external gelation: size control

External gelation process was used to prepare ceria-stabilized zirconia (CSZ) microspheres at various conditions. The effects of nozzle inner diameter, broth flow rate and Zr concentration on microsphere diameter, standard deviation (SD) of diameter and sphericity were investigated. The microsphere diameter decreased, while sphericity increased as flow rate increased. Diameter SD was low at the middle flow rate range. Diameter and sphericity increased as Zr concentration increased. Crushing strength and density increased steadily while cracking rate decreased to 0 by 0.84 mol/L. The quantified results were summarized as boundary conditions for preparation of CSZ microspheres. They were depicted into a size control diagram. The CSZ microspheres from 96 to 573 μm in size could be prepared by selecting preparation conditions according to the diagram. The effectiveness of size control was confirmed by verification experiments. The obtained CSZ microspheres were characterized by optical microscopy, scanning electron microscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM). Microscopic images showed their monodispersity, good sphericity and smooth surface. XRD and TEM results revealed their well-crystallized CSZ phase. Graphical Abstract