Effects of Thermal Annealing on Formation of Micro Porous Titanium Oxide by the Sol–Gel Method

We investigated the structural and optical properties of microporous titanium oxide (TiO2) fabricated by the sol–gel method using templates of colloidal crystals with polystyrene spheres when the annealing temperature was changed between 600° and 1000°C. From X-ray diffraction patterns and SEM images, the rutile TiO2 annealed at a high temperature did not form periodic porous bodies, while the anatase TiO2 annealed at lower than 800°C formed periodic porous bodies. The porous TiO2 obtained acts as an air-sphere/TiO2 photonic crystal with an FCC structure. It is suggested that TiO2 sol annealed at a lower temperature do not lead to phase transition from the anatase phase to the rutile phase to obtain the air-sphere/TiO2 photonic crystal by the sol–gel method using templates of colloidal crystals.