Lanthanum-doped SrTiO3 theoretical thermoelectric properties

The doped SrTiO3 as a thermoelectric material has been extensively studied both experimentally and theoretically. Though theoretical studies have found the thermoelectric coefficients changing as functions of temperature, they are less useful to guide experiments because there is no direct comparison with the existing experimental results. Combining the latest experimental results, we investigate the lanthanum nanostructure doped SrTiO3 theoretically by applying the density functional theory and the Boltzmann transport theory. For most doping levels, we find that the new Fermi levels are above the conduction band minimum, making this larger bandgap oxide metallic. The electronic acoustic phonon scattering is less important, but polar phonon and vacancy scattering become dominant. For the SrTiO3, this points to a potential approach to adjust relaxation time to optimize the thermoelectric performance by selecting doping elements with different radii. The temperature-dependent Lorentz number shows the doped compound behaves half metallic and half semiconductor. The Hall factor is conventionally taken as unity, but the calculated ones are about 0.8, independent of temperature.