Potential Thermoelectric Material Research Articles

Defective perovskites Cs2SeCl6 and Cs2TeCl6 as novel high temperature potential thermoelectric materials

On basis of our first principle calculations, we suggest lead free defective perovskites Cs2SeCl6 and Cs2TeCl6 as efficient high temperature thermoelectric materials. Our calculations predict high stability of these materials. The calculated flat valence bands in these compounds results high values of Seebeck coefficient. The density of states predicts the p-type conductivity in both compounds which was confirmed from positive value of Seebeck coefficient. The calculated thermal conductivity was found as low, 1.068 and 0.697 W/mK for Cs2SeCl6 and Cs2TeCl6, respectively at 800 K. This results high ZT values in comparison of lead halide perovskites. The combination of high electrical conductivity with Seebeck coefficient give rise to reasonable values of power factor 0.81 × 10−3 W/mK2 for Cs2SeCl6 and 0.83 × 10−3 W/mK2 for Cs2TeCl6 at 800 K. Furthermore, our calculated mechanical properties predicted the studied compounds as ductile. The ductile nature along with high values of thermoelectric parameters makes Cs2SeCl6 and Cs2TeCl6 compounds more promising for thermoelectric power generation at high temperatures.

Potential thermoelectric materials of indium and tellurium co-doped bismuth selenide single crystals grown by melt growth technique

In the present work, the thermoelectric properties of potential thermoelectric materials (Bi1−xInx)2Se2.7Te0.3 grown as high-quality single crystals by the melt growth technique were investigated between 10 and 350 K. Powder X-ray diffraction confirms the hexagonal crystal structure of all studied crystals. The high-resolution X-ray diffraction study reveals the direction of growth, single-crystal quality, dislocation density, and the influence of dopants on the inner plane structure of the crystals. A clean surface with very low angle grain boundaries is observed by the field emission scanning electron microscopy. Energy-dispersive X-ray analysis confirms the elemental composition of the crystals. Electrical resistivity has shown degenerate semiconducting behavior with low activation energy. The Seebeck coefficient confirms p-type for the pristine and n-type conducting behavior for the doped samples, with the correlation to the carrier concentration and carrier mobility in the order of 1025/m3 and 10−4 m2/V s, respectively. Thermal conductivity has shown the dominant behavior of phonon scattering. A significant reduction in the electrical resistivity was found for the co-doped (Bi0.96In0.04)2Se2.7Te0.3 sample, leading to an enhancement of the power factor (PF) and thermoelectric figure of merit (ZT) by a factor of about 8.0 and 4.1, respectively, as compared to the pristine Bi2Se3 sample at 350 K. The highest ZT value of about 0.285 is achieved for (Bi0.96In0.04)2Se2.7Te0.3 at 350 K.

Novel Deep Space Nuclear Electric Propulsion Spacecraft

The space industry is expanding at an increasing rate. While most efforts are currently focused on Earth and lunar orbits, it is only a matter of time before affordable exploration missions into deep space become more prevalent. Nuclear electric propulsion (NEP) with large quantities of power have been theorized for such missions with many advantages over traditional solar panels and radioisotope power sources. Key among NEP issues has been the power conversion system, often falling upon dynamic cycles over solid-state options like thermoelectric generators (TEGs) because of low efficiencies. Howe Industries has conceptualized a deep space probe capable of transporting cube satellites (CubeSats) and other payloads to deep space utilizing NEP based on an advanced TEG power conversion system with efficiencies that would challenge traditional dynamic power conversion cycles. Experimentation at a TRIGA research reactor has shown a potential for 20 to 50 times increase in electrical conductivity of potential thermoelectric materials, which would correlate to large increases in efficiencies over traditional TEGs.

Influence of Ternary and Quaternary Inclusion on Bandgap Tuning of CaTe: Prediction of Potential Thermoelectric Materials

The structural, optoelectronic, and thermoelectric properties of CaTe, Ca0.5Ba0.5Te, CaTe0.5Se0.5, and Ca0.5Ba0.5Te0.5Se0.5 alloys are studied using the full-potential linearized augmented plane wave method within the framework of density functional theory. The calculated ground-state properties agree well with available data. The electronic and bonding behavior of the materials is studied and further verified by electron density contours. Additionally, mechanical stability is confirmed by calculating the shear modulus, Young’s modulus, bulk modulus, and hardness values. From the brittle/ductile analysis, the newly predicted compounds are found to be less brittle (more ductile) than the parent CaTe compound. The valence band maxima and the conduction band minima (CBM) of the Ca0.5Ba0.5Te, CaTe0.5Se0.5, and Ca0.5Ba0.5Te0.5Se0.5 alloys are located at the Г point, resulting in a direct bandgap. The optical properties of the materials are calculated for the energy range of 0–13.5 eV. As expected, the highest Seebeck coefficient value is observed as 245.8 μV/K and 248.6 μV/K for CaTe0.5Se0.5 and Ca0.5Ba0.5Te0.5Se0.5 alloys, respectively, at 300 K. The present work exhibits the optoelectronic and thermoelectric properties, but the available material flexibility has various other applications.

Structural, electronic and thermoelectric performance of narrow gap LuNiSb half Heusler compound: Potential thermoelectric material

We report the band structure calculations of rare earth based half Heusler LuNiSb compound for thermoelectric performance. A narrow energy gap of 0.227 eV is opened using TB-mBJ approximation. The value of Seebeck coefficient 288 (μVK −1) at room temperature using mBJ scheme is quite large as compared to the experiment as well as well known thermoelectric material PbTe at same temperature. The observed highest value (6.1 × 10 10 Wm −1 K −2 s −1) at 647 K is close to our calculated value 9.93 × 10 10 Wm −1 K −2 s −1 at 650 K using GGA + U approximations. We found the Lu-4 f flat bands lie in conduction band along Γ– X direction are mainly responsible for maximum peaks of Power factor. The high value 0.804 of ZT and value of other thermoelectric parameters indicate that LuNiSb would be a favourable material for room temperature thermo electric applications.

Advances in the Applications of Graphene-Based Nanocomposites in Clean Energy Materials

Extensive use of fossil fuels can lead to energy depletion and serious environmental pollution. Therefore, it is necessary to solve these problems by developing clean energy. Graphene materials own the advantages of high electrocatalytic activity, high conductivity, excellent mechanical strength, strong flexibility, large specific surface area and light weight, thus giving the potential to store electric charge, ions or hydrogen. Graphene-based nanocomposites have become new research hotspots in the field of energy storage and conversion, such as in fuel cells, lithium-ion batteries, solar cells and thermoelectric conversion. Graphene as a catalyst carrier of hydrogen fuel cells has been further modified to obtain higher and more uniform metal dispersion, hence improving the electrocatalyst activity. Moreover, it can complement the network of electroactive materials to buffer the change of electrode volume and prevent the breakage and aggregation of electrode materials, and graphene oxide is also used as a cheap and sustainable proton exchange membrane. In lithium-ion batteries, substituting heteroatoms for carbon atoms in graphene composite electrodes can produce defects on the graphitized surface which have a good reversible specific capacity and increased energy and power densities. In solar cells, the performance of the interface and junction is enhanced by using a few layers of graphene-based composites and more electron-hole pairs are collected; therefore, the conversion efficiency is increased. Graphene has a high Seebeck coefficient, and therefore, it is a potential thermoelectric material. In this paper, we review the latest progress in the synthesis, characterization, evaluation and properties of graphene-based composites and their practical applications in fuel cells, lithium-ion batteries, solar cells and thermoelectric conversion.

Thermoelectric transport properties of two-dimensional materials <i>X</i>Te<sub>2</sub> (<i>X</i> = Pd, Pt) via first-principles calculations

<sec>Developing efficient thermoelectric materials has never lost the attraction due to their promising performances in the energy conversion. The different mechanisms of phonon scattering lead to the various outstanding performances of layered materials in thermoelectric properties. So we investigate the structure, electronic and thermoelectric transport properties of Penta-<i>X</i>Te<sub>2</sub> (<i>X</i> = Pd, Pt) layers based on the density functional theory and Boltzmann transport theory. Those monolayers have a beautiful penta-graphene-like buckled structure with a space group of <i>P</i>2_1/<i>c</i> (No.14). The values of optimized lattice constant <i>a</i> (<i>b</i>) are 6.437 Å (6.145 Å) and 6.423 Å (6.12 Å) for PdTe<sub>2</sub> and PtTe<sub>2</sub> monolayers, respectively. In order to assess the stability, we calculate the phonon dispersion along the high symmetry lines in the Brillouin zone. The second-order harmonic and third-order anharmonic interatomic force constants (IFCs) are calculated by using 5 × 5 × 1 supercell and 4 × 4 × 1 supercell based on the relaxed unit cell. All these results indicate that those monolayers are thermodynamically stable. Energy band structure is essential in obtaining reliable transport properties. So we calculate the band structures of penta-<i>X</i>Te<sub>2</sub>. Both PdTe<sub>2</sub> and PtTe<sub>2</sub> are semiconductors with indirect band gaps of 1.24 eV and 1.38 eV, respectively, which are in good agreement with previous experimental and theoretical results.</sec><sec>The lattice thermal conductivity of <i>X</i>Te<sub>2</sub> decreases with temperature increasing, but the electronic thermal conductivity varies with temperature in the opposite way exactly. It is found that the thermal conductivity comes from the contribution of the lattice thermal conductivity at low temperature. The room-temperature total thermal conductivities in the <i>x</i> (<i>y</i>) direction of the PdTe<sub>2</sub> and PtTe<sub>2</sub> monolayers are 3.95 W/(m·K) (2.7 W/(m·K)) and 3.27 W/(m·K)(1.04 W/(m·K)), respectively. The contribution of low thermal conductivity indicates that the thermoelectric properties of PtTe<sub>2</sub> monolayer may be better than those of PdTe<sub>2</sub> monolayer.</sec><sec>The relaxation time (<i>τ</i>) and carrier mobility (<i>μ</i>) are obtained based on the Bardeen-Shockley deformation potential (DP) theory in two-dimensional materials. Remarkably, they have the higher hole mobility than the electron mobility. The anisotropic electronic transport properties of <i>X</i>Te<sub>2</sub> are obtained by solving Boltzmann transport equation. The electrical conductivity over relaxation time (<i>σ</i>/<i>τ</i>) and Seebeck coefficient (<i>S</i>) contribute to the figure of merit <i>ZT</i>. High Seebeck coefficient (<i>S</i>) with the value larger than 400 μV/K can be found in both p-type and n-type cases, suggesting that the TE performance of <i>X</i>Te<sub>2</sub> may be considerable. The room-temperature largest <i>ZT</i> values of penta-<i>X</i>Te<sub>2</sub> (<i>X</i> = Pd, Pt) at p-type are 0.83 and 2.75 respectively. The monolayer PtTe<sub>2</sub> is a potential thermoelectric material.</sec>

Potential thermoelectric materials: first-principles prediction of low lattice thermal conductivity of two-dimensional (2D) orthogonal ScX2 (X = C and N) compounds.

Thermoelectric materials with excellent performance can efficiently and directly convert waste heat into electrical energy. In today's era, finding thermoelectric materials with excellent performance and adjusting the thermoelectric parameters are essential for the sustainable development of energy in the context of the energy crisis and global warming. Through first-principles calculations, we notice that two-dimensional (2D) orthogonal ScX2 (X = C and N) compounds show great potential in the field of thermoelectricity. Different from most materials containing C or N atoms, which are generally accompanied by high lattice thermal conductivity (TC), the 2D o-ScX2 exhibited a rather low and anisotropic lattice TC. The κ3L (the lattice thermal conductivity including the effect of three-phonon scattering and isotope scattering) of o-ScC2 along the X and Y directions are 2.79 W m-1 K-1 and 1.55 W m-1 K-1, and those of o-ScN2 are 1.57 W m-1 K-1 and 0.56 W m-1 K-1. By calculating the fourth-order interatomic force constants (IFCs), we obtain the κ3+4L with the additional four-phonon scattering effect. Our results clearly show that four-phonon scattering plays an important role in the TC of the two materials, the κ3+4L of o-ScC2 is only half of its κ3L. Furthermore, it can be noticed that the low lattice TCs of o-ScX2 (X = C and N) are the result of many factors, e.g., heavy atom doping, the strong anharmonicity caused by the vibration of Sc atoms in the out-of-plane direction and C(N) atoms in the in-plane direction, important four-phonon scattering and strongly polarized covalent bonds between X atoms and Sc atoms. Moreover, it is interesting to find that the thermal transport properties of o-ScX2 are led by a different phonon mechanism, e.g., the different TCs of o-ScC2 and o-ScN2 are determined by the anharmonic characteristic, and the harmonic characteristic plays a more important role in the anisotropy of o-ScX2 (X = C and N). In general, our research can be expected to provide important guidance for the application of o-ScX2 (X = C and N) in the thermoelectric field.

Pavonite homologues as potential n-type thermoelectric materials: crystal structure and performance

The pavonite homologous series assembled from two basic modules is a potential n-type thermoelectric material.

Thermoelectric performance of BaBiNa and SrBiNa: A first-principle study

The high thermoelectric performance is expected to develop practical thermoelectric materials. The relationship between the dimensionless figure of merit (ZT) and the carrier concentration and the temperature is constructed to identify the best thermoelectric performance of XBiNa (X = Ba and Sr). The electronic structure and transport properties of the two semiconductors are calculated by combining the first-principle DFT with the semi-classical Boltzmann transport theory to obtain the Seebeck coefficient, electronic thermal conductivity, and electrical conductivity. The relaxation time is determined by the deformation potential theory, and the lattice thermal conductivity is calculated by the Slack model. The maximum ZTs of 1.14 and 1.16 can be achieved for the n-type BaBiNa and SrBiNa at a carrier concentration of 5.62 × 1018/3.60 × 1018 cm−3 at 800 K, respectively. The maximum thermoelectric conversion efficiency of 21.25 % is attributed to the n-type SrBiNa, implying that the compound is potential thermoelectric material. The different thermoelectric mechanisms for the n- and p-type XBiNa are elucidated through evaluating the tendency of the transport coefficients and ZT.

Enhancing the Thermoelectric Performance of Mg2Sn Single Crystals via Point Defect Engineering and Sb Doping.

Mg2Sn is a potential thermoelectric (TE) material that exhibits environmental compatibility. In this study, we fabricated Sb-doped Mg2Sn (Mg2Sn1-xSbx) single-crystal ingots and demonstrated the enhancement of TE performance via point defect engineering and Sb doping. The Mg2Sn1-xSbx single-crystal ingots exhibited considerably enhanced electrical conductivity because of the donor-doping effect in addition to high carrier mobility. Moreover, the Mg2Sn1-xSbx single-crystal ingots contained Mg vacancy (VMg) as a point defect. The introduced VMg and doped Sb atoms formed nanostructures, both acting as phonon-scattering centers. Consequently, lower lattice thermal conductivity was achieved for the Mg2Sn1-xSbx single-crystal ingots compared with polycrystalline counterparts. Owing to the significant enhancement in the electrical conductivity and the reduction in the lattice thermal conductivity, the maximum power factor of 5.1(4) × 10-3 W/(K2 m) and the maximum dimensionless figure of merit of 0.72(5) were achieved for the Mg2Sn0.99Sb0.01 single-crystal ingot, which are higher than those of single-phase Mg2Sn1-xSb polycrystals.

Quartic anharmonicity and ultra‐low lattice thermal conductivity of alkali antimonide compounds M 3 Sb ( M = K, Rb and Cs)

We investigate the role of the quartic anharmonicity in lattice dynamics and the thermal transport properties of the alkali antimonide compounds M3Sb (M = K, Rb and Cs) by using the self-consistent phonon theory combined with compressive sensing techniques. We found that the alkali-metal atoms in K3Sb, Rb3Sb and Cs3Sb have a strong quartic anharmonicity and play a crucial role in the lattice dynamic stability. Based on the above results, the thermal transport properties are estimated with the relaxation time approximation of Boltzmann transport equation, the calculated lattice thermal conductivity κL shows a remarkably low value at 300 K, which is 1.26, 0.63 and 0.52 Wm−1 K−1 for K3Sb, Rb3Sb and Cs3Sb, respectively. We have demonstrated the quartic anharmonicity of alkali antimonide compounds M3Sb (M = K, Rb and Cs) and studied their thermal transport properties, which has never been reported before, the ultra-low lattice thermal conductivity indicates that K3Sb, Rb3Sb and Cs3Sb are potential thermoelectric materials.

Preparing bulk Cu-Ni-Mn based thermoelectric alloys and synergistically improving their thermoelectric and mechanical properties using nanotwins and nanoprecipitates

Cu-Ni-Mn based alloys have long been considered as potential thermoelectric materials because of their Seebeck effect and large power factor. In this study, bulk Cu-Ni-Mn based alloys with nanostructures were prepared via melting and cryorolling, and their thermoelectric and mechanical properties were analyzed. A large number of nanotwins and nanoprecipitates were observed in the prepared alloys using transmission electron microscopy. These observations indicate that the bulk Cu-Ni-Mn alloys with nanostructures can be successfully prepared using conventional melting-solidification-rolling technology. The Cu-Ni-Mn alloy containing nanotwins exhibits a promising Seebeck coefficient of ∼ −72.8 μVK−1 and power factor of ∼11000 μWm−1K−2 at 1073 K, and thereby, a high output power density. The bulk Zr-doped Cu-Ni-Mn alloy containing nanoprecipitates and nanotwins exhibits a lower thermal conductivity of ∼32.9 Wm−1K−1 and a 37.5% higher ZT of ∼0.22 at 773 K. Enhanced mechanical properties make the Cu-Ni-Mn based alloys a promising candidate for thermoelectric application. Our discovery provides a promising strategy to improve the thermoelectric and mechanical properties of materials with high thermal conductivity through the introduction of nanotwins and nanoprecipitates.

Ultralow Thermal Conductivity and Large Figure of Merit in Low-Cost and Nontoxic Core-Shell Cu@Cu2O Nanocomposites.

Identification of novel materials with enhanced thermoelectric (TE) performance is critical for advancing TE research. In this direction, this is the first report on TE properties of low-cost, nontoxic, and abundant core-shell Cu@Cu2O nanocomposites synthesized using a facile and cheap solution-phase method. They show ultralow thermal conductivity of nearly 10-3 of the copper bulk value, large thermopower of ∼373 μVK-1, and, consequently, a TE figure of merit of 0.16 at 320 K which is larger than those of many of the potential TE materials such as PbTe, SnSe, and SiGe, showing its potential for TE applications. The ultralow thermal conductivity is mainly attributed to the multiscale phonon scattering from intrinsic defects in Cu2O, grain boundaries, lattice-mismatched interface, as well as dissimilar vibrational properties. The large thermopower is associated with a sharp modulation in carrier density of states due to charge transfer between Cu and Cu2O nanoparticles and carrier energy filtering. They are tuned by varying the trioctylphosphine concentration.

Enhancement of the Electrical Conductivity and Thermoelectric Performance of Single-Walled Carbon Nanotubes by the Introduction of Conjugated Small Molecules with Cation Groups

Organic conjugated small molecules (OCSMs)-based single-walled carbon nanotube (SWCNT) composites have received great attention as potential thermoelectric (TE) materials. The studies show that both π–π and cation−π interactions between OCSMs and SWCNTs obviously improve the TE performance. However, up to now, few OCSMs containing both cation groups and π structures have been combined with SWCNTs as TE materials. In this work, an organic conjugated small molecule with a cation group, (benzotriazol-1-yloxy)tripyrrolidinophosphonium hexafluorophosphate (PyBOP), was applied to combine with SWCNTs for the first time due to π–π and cation−π interactions between PyBOP and SWCNTs, which are beneficial to improving the electrical conductivity and thermoelectric (TE) performance. The highest electrical conductivity of 3731.5 S cm–1 was achieved for SWCNT/PyBOP, which was 6.59 times larger than that of the pristine SWCNTs, and also one of the highest values for OCSM-based SWCNT composites reported up to date. Among all of the composites, SWCNT/PyBOP displays the maximum power factor of 279.5 μW m–1 K–2 at 403 K. The results demonstrate that the electrical conductivity of SWCNT composites can be dramatically improved by tuning the structure of the OCSMs, which points out a new direction for the rapid development of high-performance TE composite materials.

Vanadium-doped BaTiO3 as high performance thermoelectric material: role of electronic structure engineering

It is well known that thermoelectric (TE) materials are the most sought-after ones to mitigate energy crisis. Development of an efficient non-toxic, economic, abundant, and stable TE material is quite difficult due to its complicated traits. BaTiO3, a perovskite material shows a tremendous potential as a TE material due to its highly tunable electronic structure. Herein, for the first time we report use of dopant to improve the Seebeck coefficient of BaTiO3. We used first-principles density functional theory calculations to study the effect of vanadium doping in BaTiO3, and for the first time, we report that V acts as a resonant dopant in BaTiO3. The study on effect of site occupancy reveals that V in Ba site distorts the density of states below the conduction band by introducing resonance level at the Fermi level. The transport property calculations based on Boltzmann's relation predicts V-doped BaTiO3 to be a potential TE material. The results also provide new insights into development of BaTiO3 as a multifunctional material.

Enhanced thermoelectric properties of MnxCu1.8S via tuning band structure and scattering multiscale phonons

Digenite (Cu1.8S) as a potential p-type thermoelectric (TE) material has attracted extensive attention due to its environmental benign, abundant resources and low cost of component elements. In this study, the TE properties of MnxCu1.8S bulk samples prepared by mechanical alloying (MA) combined with spark plasma sintering (SPS) were investigated. Doping Mn would initially substitute Cu and tune the band structure of Cu1.8S with an enlarged band gap Eg. However, if Mn content is beyond the solubility limit of x = 0.01 in Cu1.8S will cause the formation of MnS, which contributes to the formation of Cu-rich phases at 0.02 ≤ x ≤ 0.08. Benefiting from the synergetic scattering effect of point defects (MnCu•, VS••) and MnS, Cu1.96S, Cu1.97S, Cu2S phases, the lowest thermal conductivity κ value of 0.75 W m−1K−1 was obtained at 773 K for Mn0.08Cu1.8S. Along with the decreased κ, the highest figure of merit ZT value of 0.92 at 773 K achieved in Mn0.08Cu1.8S bulk sample. A maximum engineering ZTeng of 0.3 and its efficiency ηmax of about 6% were obtained at 323–773 K, which is almost 3 times than that of the pristine Cu1.8S (ηmax = 2.2%). Introducing Mn in Cu1.8S is an effective and convenient strategy to improve TE performance.

The structures and thermoelectric properties of Zn-Sb alloy films fabricated by electron beam evaporation through an ion beam assisted deposition

Zn-Sb alloys are potential low-cost and non-toxic p-type thermoelectric materials for applications in the temperature range between 300 and 700 K. In this experiment, Zn-Sb alloy films were prepared by electron beam evaporation through an ion beam assisted deposition (IBAD). Our studies have confirmed that the structural phase, chemical composition, chemical binding, carrier concentration and microstructures of the film can indeed be effectively controlled by the voltage and current of the ion beam. Particularly, the carrier concentration of the film will rise along with the increase of the argon ion beam current. When the ion beam currents are set at 0.2–0.6 A, the carrier concentrations of the films can be controlled at around 1019–1020 cm−3, which fall within the optimal carrier concentration range for Zn-Sb based thermoelectric materials. The temperature dependence of Seebeck coefficient and the electrical conductivity of the films were measured to evaluate their thermoelectric performance. The results indicate that the film with Zn4Sb3 + ZnSb mixed phase will have better thermoelectric properties. A high power factor value of ~1280 μW/m-K2 is obtained in the films assisted by the ion beam current of 0.6 A. Our results demonstrate that the IBAD technique is extraordinary promising to fabricate Zn-Sb films with excellent thermoelectric performance and can be used to produce other potential thermoelectric materials.

Improved thermoelectric performance of n-type Mg3Sb2–Mg3Bi2 alloy with Co element doping

n-type Mg3Sb2–Mg3Bi2 alloy shows as a potential new thermoelectric material (TE) and has been widely researched recently. The pure phase n-type Mg3·20(Sb0·3Bi0.7)1.99Te0.01 were prepared by adjusting Mg content with the Bi impurity phase being effectively suppressed. Then, Co element was doped into the pure phase and the electrical conductivity of samples were improved. With a high power factor of 20.3 μW cm−1K−2 for Mg3·185Co0·015(Sb0·3Bi0.7)1.99Te0.01 at 525 K. Additionally, it was found that the phonon scattering is enhanced due to the larger atomic mass of Co comparing to Mg and the lattice thermal conductivity is reduced. As a result, a high ZT value of ~ 1.03 at 525 K is achieved for the Mg3·185Co0·015(Sb0·3Bi0.7)1.99Te0.01.

Structural, electronic, magnetic and thermoelectric properties of pseudobrookite-type Fe2-xTi1+xO5 (x = 0, 0.5 and 1) compounds: DFT + U approaches

The wide band-gap of iron titanium oxide Fe2TiO5 (Pseudobrookite) is very well known as potential thermoelectric compounds for its great Seebeck coefficient. In this article, the thermoelectric, magnetic, electronic, and structural properties of ferrous pseudobrookite Fe2-xTi1+xO5 (x = 0, 0.5, and 1.0) compounds were calculated by first principle calculations. The electronic structures were computed using the plane-wave pseudopotential method within the GGA-PBE approximation considering the Hubbard-U exchange-correlation. The considered electronic structure in the GGA + U scheme displays that two alloys are semiconductors with an indirect energy gap of 1.75 and 0.61 eV, respectively, for Fe2TiO5, and Fe1·5Ti1·5O5 and metallic for FeTi2O5 compounds. The thermoelectric properties were estimated using the semi-classical Boltzmann theory and the rigid band method in the temperature range of 50–800 K. The carrier concentration (n,p), electrical conductivity (σ), Seebeck coefficient (S), electronic thermal conductivity (κ) and the electric figure of merit (ZT) as a function of temperature were obtained for Fe2-xTi1+xO5 (x = 0, 0.5, and 1.0) compounds. Also, the thermoelectric properties versus chemical potential were studied at three constant temperatures. The Seebeck coefficient decreased with increasing temperature. The peak value of S is 1913 μVK−1, 1217 μVK−1, and 616 μVK−1 for Fe2TiO5, Fe1·5Ti1·5O5, and FeTi2O5, respectively. By increasing the chemical potential and moving it to the conduction electrons, the thermal conductivity increased. The results show that n-type Fe2TiO5 and p-type Fe1·5Ti1·5O5 at 300 K can reach the ZT values of 1.21 and 0.98, respectively. These results detected that n-type Fe2TiO5 compounds are potential thermoelectric material at room temperature.