Effect of microstructural features on the electrical properties of TiO2

The effect of microstructural features on the electrical properties of TiO2 (rutile) was studied using impedance spectroscopy in conjunction with X-ray diffraction and scanning electron microscopy. The electrical properties of TiO2 were measured at 350 °C after sintering in air at different temperatures. It was found that the electrical resistivity increased significantly after the interconnected pores closed in the TiO2 due to sintering. However, further decrease of porosity in the TiO2 had little effect on its resistivity prior to the closure of pores. On the other hand, after the sintered specimens were annealed in vacuum, the resistivity of TiO2 decreased considerably without apparent change of the microstructure in TiO2. Moreover, the resistivity, measured at room temperature, decreased after the interconnected pores closed due to sintering. These results suggest that the electrical conduction in TiO2 after sintering in air is mainly due to ionic conduction, while the conduction in the sintered TiO2 after annealing in vacuum was mainly due to electronic conduction. The closure of the open pores in the TiO2 reduced the surface ionic conduction but increased the electronic conduction route. Overall, the microstructural features of TiO2 have characteristic effects on its electrical properties.