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 (TiO 2 ) 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 TiO 2 annealed at a high temperature did not form periodic porous bodies, while the anatase TiO 2 annealed at lower than 800°C formed periodic porous bodies. The porous TiO 2 obtained acts as an air‐sphere/TiO 2 photonic crystal with an FCC structure. It is suggested that TiO 2 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/TiO 2 photonic crystal by the sol–gel method using templates of colloidal crystals.