A comparative study of small-size ceria–zirconia microspheres fabricated by external and internal gelation

Fabrication of ceria – zirconia (CSZ) microspheres by external gelation (EG) and internal gelation (IG) process was investigated. A nozzle with an inner diameter of 0.2 mm was used for broth dispersion under vibration. The effect of broth flow rate on diameter and sphericity of the microspheres was studied. The microspheres were characterized by thermogravimetry/differential thermal analysis, X-ray diffraction, optical microscopy, scanning electron microscopy and transmission electron microscopy. The results showed that EG microspheres had a better mono-dispersity of diameter with a variance about 30, while IG microspheres had a better sphericity of about 1.02. EG microspheres with CSZ phase and compact microstructure had higher crushing strength and density than those of IG with monoclinic zirconia phase and loose microstructure. External gelation was proved to be suitable for fabrication of small-sized CSZ microspheres. Graphical Abstract