Mesoporous-structure-tailored hydrothermal synthesis and mechanism of the SrTiO3 mesoporous spheres by controlling the silicate semipermeable membranes with the KOH concentrations

Abstract

Mesoporous structure-tailored SrTiO₃ mesoporous spheres have been hydrothermally realized by controlling the silicate semipermeable membranes with KOH concentration. The phase and microstructures were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, thermogravimetric analysis and N₂-physisorption techniques, respectively. Because the high KOH concentration lowers the polymerization degree of the silicate anion species, the silicate semipermeable membranes become thinner with increasing KOH concentration. Whereas the attenuated silicate semipermeable membranes favour the penetration of the metal ions, the primary SrTiO₃ nanocrystallites for the self-assembly of the SrTiO₃ mesoporous spheres grow larger as the KOH concentration increases. As a consequence, the mesoporous structures of the self-assembled SrTiO₃ mesoporous spheres can be simply tailored by adjusting the KOH concentration of the hydrothermal reaction system. Moreover, because the attenuation of the silicate membrane facilitates the orientation attachment of the primary nanocrystallites, the self-assembled SrTiO₃ mesoporous spheres trend to single-crystal-like with the increasing KOH concentration.