Thermoelectric properties of Nb-doped ordered mesoporous TiO ₂

Mesoporous materials have pores with diameters between 2 nm and 50 nm, the presence of which generally decreases the thermal conductivity of the material. By incorporating mesoporous structures into thermoelectric materials, the thermoelectric properties of these materials can be improved. Although TiO ₂ is an ordinary insulator, reduced TiO ₂ shows better electrical conductivity and is therefore a potential thermoelectric material. Furthermore, the addition of a dopant to TiO ₂ can improve its electrical conductivity. We hypothesized that, by doping ordered mesoporous TiO ₂ films with niobium, we would be able to minimize the thermal conductivity and maximize the electrical conductivity. To investigate the effects of Nb doping and a mesoporous structure on the thermoelectric characteristics of TiO ₂ films, Nb-doped mesoporous films were investigated using x-ray diffraction, ellipsometry, four-point probe measurements, and thermal conductivity analysis. We found that Nb doping of ordered mesoporous TiO ₂ films improved their thermoelectric properties.