A general approach to porous crystalline TiO2, SrTiO3, and BaTiO3 spheres.

Monodispersed porous crystalline TiO(2), SrTiO(3), and BaTiO(3) spheres were produced through a one-step hydrothermal process from amorphous TiO(2) spheres. The resulting samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and nitrogen sorption measurements. On the basis of the characterization results, we proposed a formation process of these porous spheres according to a mechanism analogous to the Kirkendall effect. This study provides a general way to synthesize porous titania-based spheres.