Temperature Characteristics of Raman Spectra in Nanometer Material Titanium Dioxide

Raman spectra of the nanophase titanium dioxide were examined at various annealing temperatures. The temperature dependences of the Raman modes at 702, 612, 422, 230 -250, and 152cm^-1 are discussed. The 702 cm^-1 A_2g mode belongs to first-order phonon connected to a critical nature of the selection rules with respect to the grain size. Lower anatase-rutile transition temperature 700°C is closely related to smaller grain size. The E_g mode at 422 cm^-1 at room temperature shifts upward 24 cm^-1 after successive annealing in air for one hour at 700°C, indicating the dependence of the lower mode frequency upon the larger oxygen deficiency.