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 mu(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. (c) 2007 Published by Elsevier B.V.