Electronic transport properties of SrTiO3 and its alloys: Sr1-xLaxTiO3 and SrTi1-xMxO3 (M = Nb, Ta)
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Wide band-gap oxide strontium titanate (SrTiO3) is highly recognized as potential thermoelectric material for its large Seebeck coefficient. Recently, several experimental studies emerged on how to improve the thermoelectric transport properties of SrTiO3 by doping with La and Nb. To aid this effort, a better understanding of the effect of doping on electronic structure and transport properties is essential. In this paper, the electronic transport properties of SrTiO3, Sr1-xLa xTiO3, and SrTi1-xMxO3 (M=Nb,Ta) are determined by detailed first-principles electronic band structure and Boltzmann transport calculations. Furthermore, the effect of uniaxial and simple shear deformations on the transport properties of pure strontium titanate is also investigated. For the treatment of the substitutional alloys, on-site Coulomb interaction added versions of electronic exchange and correlation functionals are preferred to obtain an accurate electronic band structure. Calculated Seebeck coefficient and its variation as a function of temperature for the alloy systems are compared with available experimental results; an excellent agreement is observed. Additionally, the electronic relaxation time and electronic contribution to thermal conductivity are predicted by fitting the calculated electrical conductivity to the experimental electrical conductivity. A significant increase in electronic thermal conductivity is observed for high carrier concentrations. Overall, the necessity of excessive carrier concentrations that can only be achieved by highly doped structures is verified. 2010 The American Physical Society.
