First-Principles Modeling of SrTiO₃Based Oxides for Thermoelectric Applications

Abstract

Using first-principles electronic structure calculations, we studied the electronic and thermoelectric properties of SrTiO3 based oxide materials and their nanostructures identifying those nanostructures which possess highly anisotropic electronic bands. We showed recently that highly anisotropic flat-and-dispersive bands can maximize the thermoelectric power factor, and at the same time they can produce low dimensional electronic transport in bulk semiconductors. Although most of the considered nanostructures show such highly anisotropic bands, their predicted thermoelectric performance is not improved over that of SrTiO3. Besides highly anisotropic character, we emphasize the importance of the large weights of electronic states participating in transport and the small effective mass of charge carriers along the transport direction. These requirements may be better achieved in binary transition metal oxides than in ABO3 perovskite oxide materials.

Effects of Octahedral Tilting on Band Structure and Thermoelectric Power Factor of Titanate Perovskites: A First-Principles Study on SrTiO3

“…The obtained cell parameter (a = 3.884 Å) and band gap (Eg = 3.59 eV) show good agreement with experimental results (a = 3.905 Å, Eg = 3.25 eV) 31,32 and previous computational results (a = 3.880 Å, Eg = 3.57 eV). 28 The obtained Ti-O bond length is 1.942 Å (= a/2). The band structure and density of states (DOS) of STO calculated with unit cell is shown in Figure S1.…”

“…26,27 The B1WC hybrid functional was chosen because it has been verified to deliver a good description of both the lattice constants and band gap of STO. 28,29 The electron basis sets were chosen from the CRYSTAL online database (Sr_HAYWSC311(1d)G_piskunov_2004 for Sr, Ti_86411(1d)G_baranek_2013_BaTiO3…”

Grain Boundary Engineering Nanostructured SrTiO3 for Thermoelectric Applications

“…In this analysis, the mean free path (l = •τ ) is the product of the average particle velocity ( ) and relaxation time (τ ), and should be shorter than any micro-structural feature (the grain size) introduced to lower the lattice thermal conductivity. The relaxation time for electrons in single crystals (which is dominated by electron-phonon scattering) is near ∼10 fs at 300 K [66], and the average electron velocity can be estimated from the thermal energy ( = √ 3k b T /m * ), 7 also at 300 K. For electrons with an inertial e ective mass of 0.5 m e [67] (estimated from the curvature of the band structure), the mean free path is estimated to be ∼1.5 nm. Therefore, the linear density of micro-structural defects (grain boundaries) should be much less than ∼1/nm to avoid lowering the electron mobility [68].…”

Polarity-field driven conductivity in SrTiO3/LaAlO3 : A hybrid functional study

“…The exchange-correlation energy is modelled with the B1-WC hybrid functional [26], which have been used in several previous studies about STO, LAO and their interfaces [14][15][16][27][28][29][30]. A Monkhorst-Pack mesh [31] of 6 × 6 × 6 special k-points is used for cubic bulk LAO and STO, ensuring a proper convergence of the total energy below 1 meV per formula unit.…”