Promising Candidate For Thermoelectric Applications Research Articles

Divacancy and resonance level enables high thermoelectric performance in n-type SnSe polycrystals

N-type polycrystalline SnSe is considered as a highly promising candidates for thermoelectric applications due to facile processing, machinability, and scalability. However, existing efforts do not enable a peak ZT value exceeding 2.0 in n-type polycrystalline SnSe. Here, we realized a significant ZT enhancement by leveraging the synergistic effects of divacancy defect and introducing resonance level into the conduction band. The resonance level and increased density of states resulting from tungsten boost the Seebeck coefficient. The combination of the enhanced electrical conductivity (achieved by increasing carrier concentration through WCl6 doping and Se vacancies) and large Seebeck coefficient lead to a high power factor. Microstructural analyses reveal that the co-existence of divacancy defects (Se vacancies and Sn vacancies) and endotaxial W- and Cl-rich nanoprecipitates scatter phonons effectively, resulting in ultralow lattice conductivity. Ultimately, a record-high peak ZT of 2.2 at 773 K is achieved in n-type SnSe0.92 + 0.03WCl6.

Exploring the physical properties of Rb2TlSbM6 (M = Cl, Br) inorganic halide perovskites for solar cell applications: A DFT study

We studied Rb2TlSbM6 (M = Cl, Br) halides using density functional theory calculations to determine their potential thermoelectric and optoelectronic properties. The stability of cubic phase halides was analyzed through Goldsmith’s tolerance factor and enthalpy of formation calculations. By analyzing the electronic characteristics, the bandgap of Rb2TlSbCl6(Eg=1.713eV) and Rb2TlSbBr6(Eg=1.713eV) were calculated with GGA-PBE potentials for improved accuracy and comparison with reported values. The high absorption coefficient of Rb2TlSbM6 (M = Cl, Br) perovskite halides in the ultraviolet spectrum and low reflectivity in the order of 20 % make them promising for optoelectronics and photovoltaic applications. The Poisson and Pugh ratio calculations suggested the ductile nature of these materials. The Boltz-TraP code was employed to investigate the thermoelectric properties of Rb2TlSbM6 (M = Cl, Br) perovskites within the temperature range of (200–850 K). The findings demonstrate that Rb2TlSbM6 (M = Cl, Br) is a promising candidate for thermoelectric applications based on its exceptional thermoelectric properties. The SLME analysis performed on Rb2TlSbCl6 and Rb2TlSbBr6 at 293 K indicates an SLME of 31.04 % and 27.53 %, respectively. This finding suggests that these materials have great potential for utilization in solar cells.

Improvement of the Thermoelectric Properties of p-Type Mg3Sb2 by Mg-Site Double Substitution.

A P-type Mg3Sb2-based Zintl phase compound has been considered a promising candidate for thermoelectric applications. Alloying, which introduces a high concentration of point defects, is particularly effective in scattering phonons and reducing lattice thermal conductivity. Herein, alloying in p-type Mg2.995Na0.005Sb2 via the introduction of elements like Yb, Eu, Ca, and Ba was realized, and the room-temperature lattice thermal conductivity has been effectively reduced to ∼1.1 W m-1 K-1. To further intensify the phonon scattering, two groups of elements (Eu and Cd, and Yb and Cd) were chosen for heavy alloying at the Mg site, and the lattice thermal conductivity of Mg1.49Eu0.5Cd1Na0.01Sb2 was further reduced to ∼0.45 W m-1 K-1. Eventually, a peak zT as high as ∼1.0 was achieved at 773 K, and the compound outperforms the previously reported p-type Mg3Sb2 compounds.

High-throughput screening of potentially ductile and low thermal conductivity ABX3 (X = S, Se, Te) thermoelectric perovskites

Chalcogenide perovskites, renowned for their low lattice thermal conductivity, have emerged as promising candidates for thermoelectric applications. Hence, we leveraged first-principles high-throughput calculations to investigate the electrical and thermal transport properties, as well as the ductility, of the chalcogenide perovskites ABX3 (X = S, Se, Te). Candidates with 30 combinations were initially screened by bandgap screening (Eg > 0.1 eV), stability assessment (Born–Huang criterion), and ductility evaluation (Pugh's ratio: G/K < 0.571, the ratio of shear modulus G to bulk modulus K) from the MatHub-3d database (176 ABX3 crystal structures, 32 kinds of space groups, and number of atoms Natom < 40). Intriguingly, weaker chemical bonding between the A and X site atom pairs gives rise to a higher ductility in the screened quasi-ductile perovskites. Furthermore, it should be noted that the low phonon group velocities confirmed the low lattice thermal conductivity of the materials. In consequence, the identification of quasi-ductile thermoelectrics, characterized by six n-type and six p-type candidates with ZT > 0.3 at 300 K, stands as the most promising candidates for application in thermoelectrics.

Carbon Nanohoops: Multiple Molecular Templates for Exploring Spectroscopic, Electronic, and Thermoelectric Properties.

A combination of density functional theory (DFT) methods and quantum transport theory (QTT) has been used to investigate the spectroscopic, electronic, and thermoelectric properties of carbon nanohoop molecules with different molecular templates. The connectivity type, along with inherent strain, impacts the transport behavior and creates a destructive quantum interference (DQI), which proves itself to be a powerful strategy to enhance the thermoelectric properties of these molecules, making them promising candidates for thermoelectric applications.

Predictive study of the new double Half-Heusler compounds Hf2FeNiSb2, Nb2Co2GaSb and ScNbCo2Sb2, promising candidates for thermoelectric applications

Predictive study of the new double Half-Heusler compounds Hf2FeNiSb2, Nb2Co2GaSb and ScNbCo2Sb2, promising candidates for thermoelectric applications

Optical and thermoelectric properties of new Janus ZnMN2 (M = Ge, Sn, Si and N = S, Se, Te) monolayers: a first-principles study.

Thermoelectric materials have received great interest because they directly tap into the vast reserves of currently underused thermal energy, in an environmentally friendly manner. In this work, we investigated the electronic, optical and thermoelectric properties of novel ZnMN2 (M = Ge, Sn, Si and N = S, Se, Te) monolayers by performing density functional theory calculations. The dynamic and thermal stabilities of ZnMN2 (M = Ge, Sn, Si and N = S, Se, Te) monolayers were confirmed by their phonon band structures and ab initio molecular dynamics (AIMD) simulations, which showed that all the studied monolayers are stable. Calculated electronic band structures showed that ZnSiTe2, ZnGeSe2, and ZnSnTe2 have a direct band gap, while the remaining monolayers have an indirect band gap. Optical properties in terms of the imaginary part of the dielectric function have also been investigated, which showed that all the first excitonic peaks lie in the visible region. Transport coefficients, such as the Seebeck coefficient (S), electrical conductivity (σ) and power factor (PF) were calculated using the Boltzmann theory and plotted against chemical potential. The results demonstrated that the peak values of the p-type region for the PF are greater than those of the n-type region. Notably, ZnSiTe2 exhibits a large PF due to its smaller Seebeck coefficient and higher electrical conductivity compared to ZnSnS2, indicating that it is a promising candidate for thermoelectric applications. Our findings reveal that ZnMN2 (M = Ge, Sn, Si and N = S, Se, Te) monolayers open up new possibilities for optoelectronics and thermoelectric device applications.

A first-principles study of ternary metal chalcogenides [formula omitted][formula omitted] for efficient thermoelectric applications empowered by machine-learning interatomic potential

Metal chalcogenides have already been recognized as promising candidates for thermoelectric applications in the past decade. This study systematically analyzes the ternary metal chalcogenide Ba2MnX3 (X = Te,Se,S) materials to check their suitability for thermoelectric applications. Ba2MnX3 materials belong to the orthorhombic and centrosymmetric Pnma space group, with Ba atoms distributed inside the three-dimensional framework of MnX4 tetrahedron units, forming a quasi-one-dimensional crystal structure. The electronic band structures of the materials investigated using density functional theory (GGA+U) reveal that the materials have direct band gaps ranging between 1.3 eV to 1.9 eV. The structural stability and phonon transport properties are studied using a combination of density functional theory and machine-learning approach. The study shows that all Ba2MnX3 materials possess low lattice thermal conductivity (κL). For Ba2MnTe3, at 700 K κL∼0.45Wm−1K−1 is the lowest achieved κL in this work. The thermoelectric transport parameters of the materials are estimated by working out the semiclassical Boltzmann transport equation. Finally, the Figure of merit (ZT) and thermoelectric conversion efficiency values of the materials are calculated. The maximum ZT≈ 0.74 at 700 K at a carrier concentration of 2.43×1020cm−3, and an efficiency ∼8% in the temperature interval 300 – 700 K is achieved for Ba2MnSe3.

Enhanced thermoelectric performance of Sb-doped Mg2Si0.4Sn0.6via doping, alloying and nanoprecipitation

With the advantages of eco-friendliness, low cost, and low density, Mg2(Si,Sn) solid solutions are promising candidates for thermoelectric applications. In this work, Sb-doped Mg2Si0.4Sn0.6 bulks were prepared with a combined method of solid-state reaction and high pressure synthesis, followed by spark plasma sintering. Our investigations show that Sb doping optimizes the carrier concentration, while Si/Sn alloying effectively suppresses the lattice thermal conductivity and induces a convergence of the two lowest-lying conduction bands. Additionally, numerous coherent Sn-rich nanoprecipitates are formed within micron-sized grains. All these factors contribute synergistically to improving the thermoelectric properties of Mg2Si0.4Sn0.6. The optimal Mg2(Si0.4Sn0.6)0.985Sb0.015 exhibits a power factor higher than 4 000 μW·m−1·K−2 and a lattice thermal conductivity less than 0.8 W·m−1·K−1 at temperatures higher than 600 K, leading to the highest ZT of 1.61 at 823 K. Current work demonstrates an effective approach to enhancing the thermoelectric performance of n-type Mg2X solid solutions through doping, alloying, and microstructure modification.

Gate voltage enhances the thermoelectric transport of quantum dots in graphene nanoribbons

Chemically derived graphene nanoribbons and quantum dots are unique nanostructures that offer more possibilities than 2D and 3D systems to tune their electronic properties due to the enhanced quantum confinement effects. This feature make them potential candidates for many technological applications, including thermoelectrics. In this work, we combined density functional theory calculations with the non-equilibrium Green’s function formalism to investigate the electronic and thermoelectric properties of recently synthesized quantum dots in graphene nanoribbons under the presence of an applied gate voltage, and for different temperatures. We find that the electronic states at the band edge are highly localized in the inner region of the quantum dot, and can be lifted to higher energies by applying a gate voltage, which subsequently enhances figure of merit. Moreover, at zero gate voltage and room temperature, we estimate the lower bound for ZT to be approximately 0.25. Interestingly, this lower bound can exceed unity by smoothly increasing the gate voltage for values above 6 V. The overall results regarding the enhancement of ZT suggest that quantum dots in graphene nanoribbons would be promising candidates for thermoelectric applications.

A DFT study of new full Heusler compound Li2MgC insights into the structural, electronic and thermoelectric properties: A high efficiency performance thermoelectric material

Structural, electronic and thermoelectric properties for full Heusler compound Li2MgC were studied using the full potential linearized augmented plane wave (FP-LAPW) method based on the density functional theory (DFT), implemented in the Wien2k package. The term of the exchange and correlation potential (XC) is treated by the generalized gradient approximation GGA and Trans-Blaha-modified Becke–Johnson (mBJ-GGA). From the various calculations, it emerges that the Cu2MnAl type structure is more suitable for this compound than that of the Hg2CuTi type structure; moreover, this compound is stable in the non-magnetic (NM) state. Furthermore, this compound exhibits a semi -conductor behavior with an indirect band gap at Γ-X direction. The calculated formation and cohesion energies are negative, which clearly and unequivocally indicates the thermodynamic stability of the compound studied and that it can be synthesized experimentally. Otherwise, this compound is characterized by a high figure of merit (ZT) (close to unity), making it a promising candidate for thermoelectric applications.

Enhancing the thermoelectric performance of β-Zn4Sb3 via progressive incorporation of Zn interstitials

Owing to the intrinsically low lattice thermal conductivity, β-Zn4Sb3 is regarded as a promising candidate for thermoelectric applications. To further improve its thermoelectric performance, it is essential to increase the carrier mobility of β-Zn4Sb3 for enhanced electrical transport. While incorporating light ions is a useful approach for this purpose, the excess Zn ions tend to segregate in as-grown samples. Here, we present a design strategy to stabilize the excess Zn ions in the interstitial sites by applying electric current and uniaxial stress, which triggers a progressive directional migration of Zn ions towards one terminal of the sample. In this Zn-enriched end, a homogeneous distribution of excess Zn interstitials was achieved, as confirmed by atom probe tomography and transmission electron microscopy at the atomic scale. As revealed by ab initio simulations, the additional electrons brought by Zn interstitials connect the separated (Sb2)4- dimers, enhancing the carrier mobility and thus the electrical conductivity. In consequence, the detached Zn-enriched section shows a much improved thermoelectric figure of merit, a very high maximum ZT of ∼1.5 at 618 K, and an average ZT of ∼1.1 between 300 and 618 K, outperforming the majority of thermoelectric materials in this temperature range.

A new semiconducting full Heusler Li2BeX (X = Si, Ge and Sn): first-principles phonon and Boltzmann calculations

The Full Potential-Linearized Augmented Plane Wave (FP-LAPW) is employed into density functional theory (DFT) within WIEN2k package to explore and investigate the thermoelectric, mechanical, electronic and structural properties of full-Heusler alloys Li2BeX (X = Si, Ge and Sn) were explored. The exchange and correlation potential are treated by different approximations: the generalized gradient approximation with Perdew–Burke–Ernzerhof scheme (GGA-PBE) and Tran–Blaha modified Becke–Johnson (mBJ-GGA). The results achieved for the electronic properties show that these compounds are semiconductor in nature with an indirect band gap, of values: 0.60 eV, 0.55 eV and 0.24 eV for Li2BeSi, Li2BeGe and Li2BeSn, respectively. In addition, these materials are mechanically stable owing to the fact that the conditions required for this mechanical stability satisfy Born’s criteria, and are of a brittle nature due to the calculated values of the ratios (B/G), on the other hand, these compounds are dynamically stable due to the non-presence of negative frequencies following the detailed study of phonons. These compounds are characterized by a high figure of merit (ZT) (close to unity) and high Seebeck coefficient (S), making them promising candidates for thermoelectric applications.

First-principles calculations to investigate structural, elastic, electronic, thermodynamic, and thermoelectric properties of CaPd3B4O12 (B = Ti, V) perovskites

This study has explored numerous physical properties of CaPd3Ti4O12 (CPTO) and CaPd3V4O12 (CPVO) quadruple perovskites employing the density functional theory (DFT) method. The calculated lattice constants show inclinable compliance with the experimental results that ensure their structural stability. The mechanical permanence of these two compounds was observed by the Born stability criteria as well. The mechanical and elastic behaviors have been rationalized to investigate elastic constants, bulk, shear, and Young’s modulus, Pugh’s ratio, Poisson’s ratio, and elastic anisotropy indexes. The ductility and anisotropic indexes confirm that both materials are ductile and anisotropic in essence. The band structure of CPTO reveals a 0.88 and 0.46 eV direct narrow band gap while using TB-mBJ and GGA-PBE potentials, respectively, which is an indication of its fascinating semiconducting nature. Whereas, CPVO perovskite exhibits a metallic character. The calculated partial density of states indicates the strong hybridization between Pd-4d and O-2p orbital electrons for CPTO, whereas Pd-4d and V-3d-O-2p for CPVO. The study of the chemical bonding nature and electronic charge distribution graph reveals the coexistence of covalent O-V/Pd bonds, ionic O-Ti/Ca bonds, as well as metallic Ti/V-Ti/V bonding for both compounds. The Fermi surface of CPVO ensures a kind of hole as well as electron faces simultaneously, indicating multifarious band characteristics. The prediction of the static real dielectric function (optical property) of CPTO at zero energy implies its promising dielectric nature. The photoconductivity and absorption coefficient of CPBO display good qualitative compliance with the consequences of band structure computations. The calculated thermodynamic properties manifest the thermodynamical stability for CPBO, whereas phonon dispersions of CPVO exhibit stable phonon dispersion in contrast to slightly unstable phonon dispersion of CPTO. The predicted Debye temperature (θD) has been utilized to correlate its topical features including thermoelectric behaviors. The studied thermoelectric transport properties of CPTO yielded a higher Seebeck coefficient (186 μV/K), power factor (11.9 μWcm−1K−2), and figure of merit (ZT) value of about 0.8 at 800 K, indicating that this material could be a promising candidate for thermoelectric applications.

Effect of biaxial strain on structural, electronic, optical and thermoelectric properties of LiNbO3: Ab-initio calculations

The theoretical effects of biaxial strain on the structural, electronic, optical, and thermoelectric properties of LiNbO3 were investigated using the Wien2k and BoltzTraP programs with the GGA approximation. The lattice thermal conductivity was calculated by the GIBBS code. We demonstrate that the bandgap value decreases and increase with the tensile and compressive strain respectively. The optical absorption and the optical conductivity of LiNbO3 can be enhanced by applying tensile biaxial strain. The thermoelectric properties are also investigated. LiNbO3 pure and under the biaxial strain is a p-type material. Our compounds are promising candidates for thermoelectric applications.

Thermoelectric properties of Sm-doped BiCuSeO oxyselenides fabricated by two-step reactive sintering

Among layered oxygen-containing compounds, BiCuSeO is one of the most promising candidates for thermoelectric applications due to its intrinsically low thermal conductivity and good thermal stability. However, the rather poor electrical conductivity of pristine BiCuSeO hinders its potential. Further enhancement of the thermoelectric performance by single doping at Bi site is limited mainly due to dramatic decrease of carrier mobility. Thus, new strategies, such as dual doping or doping with variable-valence elements seem to be promising. Along with that, the development of a fast and scalable synthesis route is essential for the industrial-scale fabrication of thermoelectric materials. Hence, in this paper, Bi 1– x Sm x CuSeO samples (0 ≤ x ≤ 0.08) have been synthesized with a simple and scalable reactive sintering process. For comparison, Bi 1– x Sm x CuSeO oxyselenides were also obtained by the conventional solid-state route. Our results highlight that, Sm for Bi substitution increases the electrical conductivity by 1.5–2 times and decreases the Seebeck coefficient by ~1.4 times at 873 K for both series. Overall, considering the increase of lattice thermal conductivity upon doping and not optimized power factor, the figure of merit z T is reducing upon doping. • Sm-doped BiCuSeO oxyselenides fabricated by reactive sintering. • Sm doping leads to an increase of σ from 39 Ω –1 cm –1 to ~55 Ω –1 cm –1 at 873 K. • Quality factor is reduced upon Sm doping due to increase in κ and decrease of μ w .

Nanostructured Sb2Te3 films composited with Bi2S3 for p–n conduction type conversion

The crystallization of p-type Sb2Te3 material can be tuned deterministically through compositing with n-type Bi2S3. The underlying changes in conduction from p-type to n-type are due to the crystallization changes induced by the composited Bi2S3 and the simultaneous changes in crystalline phase type. Bi2S3 nanoprecipitate formation and crystallization transition could effectively stimulate the p–n conduction transition. Upon annealing, pure Sb2Te3 partially crystallizes from the as-deposited state, which exhibits continuous crystallization during annealing. The formation of the p-type Sb2Te3 phase and the Sb2O3 phase in pure Sb2Te3 films through oxidation is significantly suppressed through compositing with excess Bi2S3. Moreover, the crystallization temperatures of the Sb2Te3–Bi2S3 films exceed 200 ℃, and the Seebeck coefficients and carrier concentrations of the samples are larger than those of pure Sb2Te3. The X-ray diffraction and Raman spectroscopy characterization of the crystalline thin films reveals a local change of the bonding arrangement around Sb atoms during crystallization. Our results suggest that Sb2Te3–Bi2S3 can serve as a promising candidate for thermoelectric applications based on n-type conduction.

First principles study of the structural stability, lattice dynamics, optical and thermoelectric properties of NaSrX(X = As, Sb and Bi)

First principles methods are utilized in exploring the structural stability, electronic, optical, phonon, thermal properties and electronic transport coefficients of NaSrX materials. Based on the calculated cohesive and formation energies, NaSrX compounds are found to be energetically stable. NaSrX materials are also shown to be direct band gap semiconductors with strong exciton binding energies between ∼0.13 and 0.20 eV. The dynamical and mechanical stabilities of NaSrX materials are further confirmed from their phonon dispersion curves and elastic constants. The calculated lattice thermal conductivities, κL, for NaSrX compounds exhibit anisotropic behaviour with the lowest value of κL found in the a-direction. Moreover, NaSrBi is shown to possess the lowest average value of κL (1.29 Wm−1K−1) as compared to NaSrAs and NaSrSb at 300 K. p-doped NaSrX compounds are shown to record large values of thermoelectric figure of merits. For instance, the highest calculated figure of merit (ZT) for p-doped NaSrAs is estimated to be 1.66 at 1200 K when p = 1020 cm−3 whereas those of NaSrSb and NaSrBi are 2.78 (at 1000 K) and 3.16 (at 900 K) respectively when p = 1019 cm−3. The large ZT values obtained in these calculations indicate that NaSrX compounds are promising candidates for thermoelectric applications.

Investigation of structural, magneto-electronic, elastic, mechanical and thermoelectric properties of novel lead-free halide double perovskite Cs2AgFeCl6: First-principles calcuations

The structural, elastic, mechanical, magneto-electronic and thermoelectric properties of Cs2AgFeCl6 lead-free halide double perovskite have been extracted and explored by a cohesive analysis using spin-polarized Density Functional Theory (DFT) associated with Boltzmann transport scheme. The exchange-correlation potential is determined through the generalized gradient approximation (GGA) and modified Becke-Johnson (mBJ). It is crystallized into cubic structure of ferromagnetic phase. The lattice parameter is estimated to be close to experimental data. The Cs2AgFeCl6 illustrates p-type ferromagnetic semiconducting properties. The 5 μB is estimated to have total magnetic moment with a necessary contribution for Fe atoms. The elastic properties prove that Cs2AgFeCl6 is stable and ductile. The thermoelectric properties of Cs2AgFeCl6 utilizing equations of Boltzmann transport through DFT into range, 100–900 K are calculated. The transport properties as figure of merit, power factor, electrical conductivity, electrical thermal conductivity and Seebeck coefficient are combined to evaluate its thermoelectric response. According to our findings, it is demonstrated that Cs2AgFeCl6 is a promising candidate for thermoelectric applications at both high and low temperatures.

CoFeVSb: A promising candidate for spin valve and thermoelectric applications

We report a combined theoretical and experimental study of a novel quaternary Heusler system CoFeVSb from the view point of room temperature spintronics and thermoelectric applications. It crystallizes in cubic structure with small DO$_3$-type disorder. The presence of disorder is confirmed by room temperature synchrotron X-ray diffraction(XRD) and extended X-ray absorption fine structure (EXAFS) measurements. Magnetization data reveal high ordering temperature with a saturation magnetization of 2.2 $\mu_B$/f.u. Resistivity measurements reflect half-metallic nature. Double hysteresis loop along with asymmetry in the magnetoresistance(MR) data reveals room temperature spin-valve feature, which remains stable even at 300 K. Hall measurements show anomalous behavior with significant contribution from intrinsic Berry phase. This compound also large room temperature power factor ($\sim0.62$ mWatt/m/K$^{2}$) and ultra low lattice thermal conductivity ($\sim0.4$ W/m/K), making it a promising candidate for thermoelectric application. Ab-initio calculations suggest weak half-metallic behavior and reduced magnetization (in agreement with experiment) in presence of DO$_3$ disorder. We have also found an energetically competing ferromagnetic FM)/antiferromagnetic (AFM) interface structure within an otherwise FM matrix: one of the prerequisites for spin valve behavior. Coexistence of so many promising features in a single system is rare, and hence CoFeVSb gives a fertile platform to explore numerous applications in future.