Transport properties of polycrystalline TiO₂ and Ti₂O₃ as semiconducting oxides

The crystal structure, electrical conductivity, Hall effect and thermoelectric power were studied for the titanium oxides (TiO₂ and Ti₂O₃). Analytical calculations of the structure using X-ray diffraction showed that TiO₂ crystallizes in tetragonal (rutile) and Ti₂O₃ in rhombohedral (corundum). Values of the calculated lattice parameters are determined. The dependence of the electrical conductivity versus the inverse of temperature was studied in the temperature range (148-373 K). The activation energy was determined for different domains of temperature. Values of Hall mobility μ_H and carrier concentration P of these oxides as a function of temperature were determined and reported. Thermoelectric power was measured for the investigated samples in the same investigated range of temperature. The results of thermoelectric power showed that the conduction can be regarded as p-type in the range from 175 to 299 K for TiO₂ and after that the conduction is n-type. While for Ti₂O₃, the negative value of thermo-power within the whole temperature range indicates that electrons are the majority carriers over the investigated range of temperature.