Thermoelectric Properties Of SrTiO3 Research Articles

Ag doping effect on electronic and thermoelectric properties of SrTiO3 (0 0 1) surface

The search for sustainable energy sources has been a global demand in recent decades. In this context, thermoelectric materials (TE) have been an interesting alternative for this purpose and constitute a relevant research topic for increasing the efficiency of sustainable energy production. In this sense, computational simulation of the functionalization of SrTiO3 is proposed via Ag-doping on the (001) surface. The results show the emergence of a midgap trap state, leading to a band gap energy decrease, an increase in dielectric constants and the effective mass electron. The Ag-doping generates a decrease in electrical conductivity and an increase in the figure of merit, which are associated with a significant reduction in thermal conductivity (∼5 times), indicating that the material can be used with TE at high temperatures. The Ag-SrTiO3 (001) surface is promising for developing new thermoelectric devices.

Suppression of intrinsic thermal conductivity in Sr1-x Gd x TiO3 ceramics via phonon-point defect scattering for enhanced thermoelectric application.

A substantial reduction in the thermal conductivity for strontium titanate (ABO3) perovskite structure was realized for the A-site substitution of gadolinium (rare earth element) in SrTiO3 ceramics. The effect of Gd3+ substitution on the structure, composition, and thermoelectric properties of SrTiO3 was investigated. The substitution of Gd3+ in the SrTiO3 matrix resulted in the minimalization of thermal conductivity. The thermal conductivity followed a similar trend as that of thermal diffusivity, but specific heat capacity exhibited a non-monotonic trend. The thermal conductivity is reduced to 1.05 W m-1 K-1 for the minimal substitutional composition (Sr0.99Gd0.01TiO3) which is 30% less than that of SrTiO3 at 303 K. The variation in the ionic radii and atomic mass of the heavier rare earth Gd3+ substituted over Sr2+ resulted in the reduction of thermal conductivity of SGTO ceramics caused by the corresponding boundary scattering at low temperatures and temperature-independent phonon-impurity scattering at high temperatures.

Effect of annealing temperature in carbon powder on thermoelectric properties of the SrTiO3−δ single crystal in the [111] crystal orientation

SrTiO3 is a promising thermoelectric material for applications in harsh environments, owing to its excellent thermoelectric (TE) properties and high-temperature stability. The effect of annealing in carbon powders on the TE properties of SrTiO3−δ in the [111] direction was experimentally investigated and analysed using first-principles calculation. The electrical conductivity of the SrTiO3−δ single crystals in the [111] direction increases with an increase in annealing temperature in the range of 1573–1673 K, which is opposite to that in the [510] direction as shown in a previous experiment. This is attributed to the different variation trend of carrier concentration. First-principle calculation results show that the carrier concentration in the [111] direction increases with increasing oxygen vacancy concentration, but it is the opposite in the [510] direction. Strong anisotropy of carrier concentration should be caused by the difference in atomic arrangement, making difference in the amount of free electrons that maybe constrained at high oxygen vacancy in different directions. Although the SrTiO3−δ single crystal annealed at 1573 K shows a lower electrical conductivity, it obtains higher power factor with the maximum value of 2.24 mW m−1 K−2 at 323 K, which is predominantly due to its higher effective mass. It also yields the highest ZT value of 0.18 at 873 K owing to the lower thermal conductivity. The results of this study are imperative for the design and development of perovskite TE materials.

Effect of La3+, Ag+ and Bi3+ doping on thermoelectric properties of SrTiO3: First-principles investigation

First principles calculations were applied to study the thermoelectric properties of La3+-, Ag+- and Bi3+- doped SrTiO3. With the exception of Sr0.9La0.1TiO3, the band gaps of Sr0.8La0.1Ag0.1TiO3, Sr0.8La0.1Bi0.1TiO3 and Sr0.7La0.1Ag0.1Bi0.1TiO3 were higher than that of SrTiO3. La3+, Ag+, and Bi3+ doping can cause an increase in electrical conductivity and power factor, and a decrease in thermal conductivity, which improves the ZT. The thermal conductivities of SrTiO3, Sr0.9La0.1TiO3, Sr0.8La0.1Ag0.1TiO3, Sr0.8La0.1Bi0.1TiO3 and Sr0.7La0.1Ag0.1Bi0.1TiO3 successively decreased, while power factor and ZT increased. Sr0.7La0.1Ag0.1Bi0.1TiO3, in particular, has the smallest thermal conductivity (2.237 W/m/K), the highest power factor (1.18 mW/(mK2)) and ZT (0.597) at 1200 K, 2.195 times larger than that of SrTiO3 (0.272). In addition, the solid state reaction method was applied to prepare dense ceramics of 10 wt% Bi-doped and (Bi, Ag)-codoped Sr0.9La0.1TiO3. It is demonstrated that (Bi, Ag)-codoped Sr0.9La0.1TiO3 have improved power factors, thermal conductivities and ZT values. The calculations and experimental results are consistent. This work demonstrates a method of co-doping Bi3+, Ag+, and La3+ to enhance the thermoelectric performance of SrTiO3.

The effect of annealing in carbon powders on the anisotropy of the thermoelectric properties of SrTiO3−δ single crystals on the (001) crystal plane

The anisotropy of the thermoelectric properties of SrTiO3 on the (001) crystal plane is investigated by a combination of first-principles calculations and experimental results.

Effect of TiO2 additive on thermoelectric properties of SrTiO3

Strontium titanate ([Formula: see text] has the advantages of being non-toxic, environmentally friendly and high-temperature stable, and has potential application in waste heat power generation at medium and high temperature. To explore the impact of TiO2 on the thermoelectric properties of SrTiO3, we synthesized TiO2/La10Nbb10-STO composite powders by hydrothermal method using precursor solution of 10[Formula: see text]mol.% La and 10[Formula: see text]mol.% Nb co-doped STO (La10Nb10-STO) containing TiO2 nanopowders with different molar ratio. After cold pressing and sintering, composite bulk materials were obtained, and their microstructure and thermoelectric transport properties were analyzed. With the increasing TiO2, although the thermal conductivity of TiO2/La10Nb10-STO composite decreased and the Seebeck coefficient increased, the minimum thermal conductivity and the maximum Seebeck coefficient were 2.54[Formula: see text][Formula: see text][Formula: see text] and 215[Formula: see text][Formula: see text]V[Formula: see text][Formula: see text], respectively, at 1000[Formula: see text]K, but the power factor decreased at high temperature due to the apparent decrease of electrical conductivity, resulting in the ZT values being lower than that of La0Nb10-STO without TiO2 addition at high temperature. Significantly, the addition of TiO2 can improve the thermoelectric performance of strontium titanate at low temperature. This approach is expected to improve the ZT of SrTiO3-based thermoelectric material through additional controlling of electrical conductivity.

Electronic and Thermoelectric Properties of SrTiO3

Background: The Thermoelectric (TE) materials and devices have been receiving much attention over past few decades due to their capacity and conversion between electrical energy and heat energy. The performance of thermoelectric materials can be estimated by the dimensionless figure of merit (ZT) and it is expressed as, ZT = σ S2T /κ. So researchers are seeking for TE materials with high figure of merit. It is well known that density functional theory calculations and Boltzmann transport theory are suitable methods for predicting TE properties. Strontium titanate (SrTiO3) is the model system for thermoelectric enhancement on Perovskite based oxides. It contains nontoxic and environment friendly substances as compared with other thermoelectric systems. Keywords: Strontium titanate, electronic structure, transport properties, quantum Espresso, DFT, GGA, wannier 90.

Theoretical Enhancement of Thermoelectric Properties of Sr1–xLaxTiO3

The electronic structure and density of state (DOS) of Sr1–xLaxTiO3 (x = 0, 0.06, 0.125, and 0.25) have been investigated on the first principle molecular orbital calculation. The La was substituted Sr site in SrTiO3 and caused an increase of electrical conductivity. The electronic structure, DOS and band structure of Sr1–xLaxTiO3 (x = 0, 0.06, 0.13, and 0.25) were calculated by discrete variational (DV)-Xα method and Material studio to estimated the thermoelectric properties. The Seebeck coefficient and electrical conductivity of Sr1–xLaxTiO3 were estimated form DOS by Boltzmann theory: Mott and Jones equation. It was found that, the substitution of La made high electrical conductivity, made high power factor and enhancement thermoelectric properties. The Sr0.87La0.13TiO3 cluster shows maximum power factor about 2.55×10−3 W/m·K2 at 1200 K. For maximum enhancement thermoelectric properties of SrTiO3 x = 0.13 should be used in the synthesis of Sr1-xLaxTiO3.

Effect of strain on thermoelectric properties of SrTiO3: First-principles calculations

The electronic structures of strained SrTiO3 were investigated by using first-principles calculations, and the anisotropic thermoelectric properties of n-type SrTiO3 under biaxial strain were calculated on the base of the semi-classical Boltzmann transport theory. It was theoretically found that the in-plane and out-of-plane power factors of n-type SrTiO3 can be increased under compressive and tensile strains, respectively, and such dependence can be explained by the strain-induced redistribution of electrons. To further optimize the thermoelectric performance of n-type SrTiO3, the maximum power factors and the corresponding optimal n-type doping levels were evaluated.

Thermoelectric Properties of SrTiO3: Bulks, Superlattices, and Transistors

Here I review the thermoelectric properties of electron doped SrTiO3. Since density of states effective mass of electron carrier in SrTiO3 crystal is rather large, heavily electron doped SrTiO3 crystal exhibits rather large Seebeck coefficient (S). The reliable thermoelectric figure of merit, ZT is ∼0.08 at room temperature and ∼0.3 at 1,000 K, which is highest among metallic oxides. Recently, we found that high-density (∼1021 cm-3) two-dimensional (2D) electron layers in SrTiO3 crystal exhibits giant S, which is ∼5 times larger than that of simple bulk, when the layer thickness is as thin as one unit cell (0.3905 nm). The 2D electron layer is realized by superlattices of SrTiO3/SrTi0.8Nb0.2O3 or TiO2/SrTiO3 heterointerface. Very recently, we fabricated high performance field effect transistors (FETs) on SrTiO3 single crystal to modulate the Seebeck coefficient by applying the gate voltage.

Thermoelectric properties of B-doped SrTiO3 singe crystal

Effect of boron on the electric and thermoelectric properties of SrTiO3 has been studied. Boron-doped SrTiO3 was prepared by vacuum annealing of SrTiO3 single crystals in presence of boron vapors. The crystals show low resistivity ∼0.1 Ω∣cm and high Seebeck coefficient of several hundreds μV/K at a room temperature. It was estimated that almost every boron atom incorporated in SrTiO3 crystal provided a charge carrier. Temperature dependence of Seebeck coefficient and figure of merit ZT were measured as a function of carrier concentration.