Size and strain dependent anatase to rutile phase transition in TiO_2 due to Si incorporation

摘要

Powders with compositions Ti_(1_x)Si_xO_2 (where 0≤x≤0.25) were prepared to systematically study the effects of Si doping on anatase to rutile phase transformation. Samples were synthesized using a modified sol-gel route and were heat treated at various temperature in 450-950 ℃ range. XRD, Raman Spectroscopy, UV-vis spectroscopy, SEM, TEM were used to study the effects of dopant concentration and heat-treatments on the crystal structure, crystallite size and particle size. Rutile phase was found to occur only above a critical crystallite size. 5/ doping was found to delay the onset of anatase to rutile phase transformation from 500 ℃ (for composition x = 0) to 800 ℃ (for x = 0.25) through the lattice strain and crystallize size modification. Interplay between the average crystallite sizes, lattice strain, annealing temperature, and their effect on phase transition are discussed in terms of Si incorporation in lattice.