Properties Of N/Y Doped Titanium Dioxide Thin Films

As a kind of n-type semiconductors, TiO2possesses good photocatalysis and hydrophilic performance. So it has been widely used in several areas, such as sewage treatment, air purification and self-cleaning antifog type glass. In practical application, TiO2has the following defects:1) the low photocatalytic quantum efficiency;2) the low solar energy utilization;3) the immobilization and recovery of catalyst. In this paper, with ordinary glass as substrate, sol-gel method is employed to prepare TiO2thin film by N doped, rare earth Y doped and N/Y co-doped.The morphology and structure of the thin films were characterized by scanning electron microscope (SEM), X-ray diffraction(XRD), UV-visible spectrophotometer(UV-VIS) and Fourier transform infrared(FTIR), at the same time, the photocatalysis and hydrophilic performance are tested by UV-VIS and optical contact angle tester, respectively. It was concluded that:(1) N dopant can suppress the transition of crystal phase; after moderate N is doped, obvious red shifting of TiO2has taken place in the absorption spectra. And the absorption strength in the UV region and the visible region is enhanced, at the same time, the size of the particles also has to grow up accordingly; with the increment of N doping, properties of the films decrease after strengthen first. When heat treatment is450℃, The photocatalytic performance of N/TiO2(11at%N), whose degradation rate is about twice higher than it of pure TiO2, is best. When the calcination temperature is500℃, the hydrophilic performance of N/TiO2(11at%N) is best, and the contact angle is only7.5°.(2) Y dopant can suppress the transition of crystal phase; after moderate Y is doped, obvious red shifting of TiO2has taken place in the absorption spectra. And the absorption strength in the UV region and the visible region is enhanced, at the same time, the size of the particles also has to corresponding reduced; with the increment of Y doping, properties of the thin films decrease after strengthen first. The photocatalytic performance of Y/TiO2(6at%Y) with heat treatment at450℃is best, and the degradation of methylene blue rate reaches61.18%. When the calcination temperature is500℃, the hydrophilic performance of Y/TiO2(6at%Y) is best, and the contact angle is only11.3°.(3) Y/N dopant suppresses anatase to rutile type, after which, the absorption spectra of doped TiO2does not change significantly. With the increase of Y/N molar ratio, the size of particle is larger after decreases first, and the properties of the films become weak after strengthen first. When the molar ratio of Y/N is6and the calcination temperature is500℃, the degradation rate of methylene blue reaches99.99%. When the calcination temperature is450℃, the hydrophilic of Y/TiO2is best, and the contact angle is only6.2°. On the other hand, as the calcination temperature rises, reunion phenomenon on the surface of the film becomes more serious, and properties of the film increase first, then decrease.