The crystal structure regulation of Ti3O5 by Al2O3 doping and its effect on the optical properties of TiO2 films prepared by electron beam evaporation were systematically studied. Ti3O5 coating materials with different Al2O3 doping contents (0–50 at%) were prepared by vacuum melting, and the corresponding TiO2 films were deposited on K9 glass substrates via electron beam vacuum evaporation. The phase structure, phase transition temperature, chemical composition and optical properties of the materials and films were characterized by XRD, DSC, EDS, XPS, UV-Vis and AFM. Results show that Al2O3 doping induces the phase transition of Ti3O5 from a room-temperature stable β-phase to a high-temperature stable λ-phase, with complete transition at 5 at% doping. Al3+ with a smaller ionic radius causes lattice contraction and local distortion of Ti3O5, enabling stabilization at room temperature of the λ-phase. For TiO2 films, 12.5 at% doping is the optimal state with the stable composition transfer under this condition. With the increase in Al2O3 doping content, the refractive index and extinction coefficient of TiO2 films decrease continuously, while the optical band gap and surface roughness show an increasing trend. The changes in optical properties are mainly ascribed to the low refractive index of Al2O3, lattice compressive strain effect and oxygen vacancy passivation induced by Al3+. This study clarifies the regulation effect of Al2O3 doping on Ti3O5 phase transition and TiO2 film optical properties, and provides theoretical basis and experimental reference for the doping modification of TiO2 films and their practical applications in consumer electronics and optical filter devices.
Peng et al. (Fri,) studied this question.