A study on the electronic properties of A site and B site doped SrTiO₃ for thermoelectric applications using first-principles calculations

Abstract

In SrTiO3, the nature of dopants and their substitution at the A or B site becomes a critical factor in determining the electrical conductivity, Seebeck coefficient, and thermal conductivity. The electronic band structure and the density of states (DOS) for the ab-initio study using different dopants were estimated using PBE-GGA approximation. The size, site of substitution, and nature of dopants cause significant changes in the lattice dimensions, band structure, band curvatures, and the density of states, which reflect as changes in the effective mass m B i ⁎ . The effective mass m B i ⁎ is calculated from the curvature of the bottom-most conduction band using the one-band effective mass approximation. Pentavalent substitutions on the B site of SrTiO3 affect the conduction band’s curvature differently than with trivalent substitutions on the A site. They also exhibit an opposite trend in the change in band curvature according to the dopant’s ionic radius. In contrast, isovalent dopants showed no change in the band curvature except for the bandgap modification. In this paper, we have provided a semi-quantitative understanding regarding the thermoelectric properties like conductivity and Seebeck coefficient that get affected due to the substituent’s nature and site at which it substitutes.

Controlling Precipitation and Dopant Effects To Achieve Promising Thermoelectric Performance in CaTiO3

“…This phenomenon enables the material to exhibit high conductivity . Nb doping leads to the gradual flattening of the lowest band near the Γ point, resulting in an increased effective mass . For the Nb25 sample, there is a slight increase in the curvature of the lowest conduction band near the Γ point compared to that of the Nb15 and Nb20 samples.…”

“…Nb substitution in CaTiO 3 facilitates hybridization between the Nb 4 d and Ti 3 d states, improving the electronic properties of CaTiO 3 . Moreover, the introduction of Nb dopants leads to a gradual flattening of the lowest band near the Γ point, resulting in an increased effective mass . Consequently, these effects enhance the Seebeck coefficient, and thus, thermoelectric properties of CaTiO 3 are enhanced.…”

“…Moreover, the introduction of Nb dopants leads to a gradual flattening of the lowest band near the Γ point, resulting in an increased effective mass. 25 Consequently, these effects enhance the Seebeck coefficient, and thus, thermoelectric properties of CaTiO 3 are enhanced. However, Nb as the primary dopant 24 in CaTiO 3 does not demonstrate exceptional electronic properties when compared with A-site doping.…”