The preparation and electrical properties of tio_{2- x} f_x

The substitution of fluorine for oxygen in TiO₂ was investigated by the reaction of Ti₂O₃, TiO₂, and TiF₃ under conditions of 4-6.5 GPa and 700–1400 °C. The single phase of TiO_2-x F_x solid solution was obtained in the region of 0≤x≤0.7. According to the x-ray diffraction data, the a and c axes of the rutile-type structure linearly increased with increasing fluorine content. The electrical resistivities of TiO₂-x F_X were in the range from 10 Ω _cm for x=0.3 to 850 Ω_cm for x = 0.7 at 300 K and the relationship between In p and 1000/T was linear. The activation energies were estimated to be from 0.17eV at x = 0.3 to 0.28 eV at x = 0.7. Also, the thermoelectric powers at room temperature changed from — 250 μV/K to + 50μV/K. The mechanism of electric conduction was discussed on the basis of the extended band model of rutile.