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The discovery of band convergence has opened an effective avenue for significantly enhancing thermoelectric performance of SnTe, while alloying CdTe in SnTe is evidenced efficient for improving the valley degeneracy. However, the thermoelectric transport properties are limited due to the low solubility of CdTe in SnTe (∼3%). Inspired by the improvement of dimensionless figure of merit zT in Cu or Se-doped SnTe, investigating the effect of Cu2Se on the electronic and phonon transport properties of SnTe-CdTe alloys is highly desired. Traditionally, improving the quality factor can trigger an increase of the potential of a compound for higher zT, which is of importance for design of thermoelectric materials. Here, alloyed 3% Cu2Se in SnTe-3%CdTe system enables an increased peak zT, which is attributed by the optimization of electronic performance (∼21 μW cm−1 K-2 at 800 K), as well as the decreased lattice thermal conductivity owing to the enhanced mass and strain fluctuations. More importantly, alloying Cu2Se not only improves the quality factor from ∼0.25 to ∼0.45, resulting in a higher maximum potential zT, but also effectively preserves the Fermi energy in a relative optimized level. The current findings demonstrate the role of Cu2Se for manipulating thermoelectrics in SnTe.

TiFe0.5Ni0.5Sb-based half-Heusler compounds have the intrinsic low lattice thermal conductivity and the adjustable band structure. Inspired by the previously reports to achieve both p- and n-type components by tuning the ratio of Fe and Ni based on the same parent TiFe0.5Ni0.5Sb, we selected Co as the amphoteric dopants to prepare both n-type and p-type pseudo-ternary Ti(Fe, Co, Ni)Sb-based half-Heusler alloys. The carrier concentration, as well as the density of states effective mass was significantly increased by Co doping, contributing to the enhanced power factor of 1.80 mW m−1 K−2 for n-type TiFe0.3Co0.2Ni0.5Sb and 2.21 mW m−1 K−2 for p-type TiFe0.5Co0.15Ni0.35Sb at 973 K. Combined with the further decreased lattice thermal conductivity due to the strain field and mass fluctuation scattering induced by alloying Hf on the Ti site, peak ZTs of 0.65 in n-type Ti0.8Hf0.2Fe0.3Co0.2Ni0.5Sb and 0.85 in p-type Ti0.8Hf0.2Fe0.5Co0.15Ni0.35Sb were achieved at 973 K, which is of great significance for the thermoelectric power generation applications.

Polycrystalline SnSe materials with ZT values comparable to those of SnSe crystals are greatly desired due to facile processing, machinability, and scale-up application. Here manipulating interatom...

Low-dimensional materials attract extensive interest in electronic applications since the synthesis of graphene. Understanding the thermal transport in low-dimensional materials with shrinking char...

Understanding the origin of intrinsic lattice thermal conductivity in crystalline solids is critical to research fields ranging from thermoelectric materials to thermal barrier coatings. This work ...

C60/Cu2Se thermoelectric nanocomposites were synthesized with various amounts of fullerene (C60; 0.03, 0.3, 0.5, 0.7 mol%) incorporated in Cu2Se. The thermoelectric figures of merits (zT) of the C60/Cu2Se nanocomposites were enhanced by 20–30% compared to that of pure Cu2Se, reaching a value of 1.4 at 773 K. The primary cause of zT enhancement is the synergetic effect of thermal conductivity reduction by phonon scattering and Seebeck coefficient increase by carrier localization that results from incorporation of C60 nanoparticles. Theoretical calculations for Seebeck coefficient enhancement and lattice thermal conductivity reduction were performed. The Seebeck coefficients of C60/Cu2Se nanocomposites were around 43% higher than that of pure Cu2Se, whereas the reduction of lattice thermal conductivity with incorporation of C60 was around 40–50%.

GeTe-based solid solutions, exemplified by GeTe–AgSbTe2 (TAGS), have revealed superior thermoelectric performance in the past few decades. Recently, alloying GeTe with other compounds in the I–V–VI2 family has been employed as an effective means to further enhance figures-of-merit. The following work has systematically investigated the alloying effect of I–V–VI2 compounds (I = Cu and Na; V = Sb and Bi; VI = Te) on the thermoelectric performance of GeTe. It has been found that all these alloying compounds can synergistically optimize the carrier concentration and reduce lattice thermal conductivity, which boosts the figure-of-merit for GeTe. More importantly, this work has demonstrated that the electronegativity difference between group I elements and Ge determines the alloy scattering potential and thus carrier mobility. As a result, compounds with nominal compositions of (GeTe)0.92(NaSbTe2)0.08 and (GeTe)0.92(CuSbTe2)0.08 have achieved zTs of ∼1.30 and 1.58 at 773 K, respectively. Our work highlights the importance of electronegativity in thermoelectric GeTe-based solid solutions and thus provides valuable guidance for designing novel thermoelectric materials.

Introduction:A new approach for expressing the lattice thermal conductivity of diatomic nanoscale materials is developed.Methods:The lattice thermal conductivity of two samples of GaAs nanobeam at 4-100K is calculated on the basis of monatomic dispersion relation. Phonons are scattered by nanobeam boundaries, point defects and other phonons via normal and Umklapp processes.Methods:A comparative study of the results of the present analysis and those obtained using Callaway formula is performed. We clearly demonstrate the importance of the utilised scattering mechanisms in lattice thermal conductivity by addressing the separate role of the phonon scattering relaxation rate. The formulas derived from the correction term are also presented, and their difference from Callaway model is evident. Furthermore their percentage contribution is sufficiently small to be neglected in calculating lattice thermal conductivity.Conclusion:Our model is successfully used to correlate the predicted lattice thermal conductivity with that of the experimental observation.

The presence of lone-pair electrons (LPE) is known to lead to large anharmonicities in materials and thus to low lattice thermal conductivity (κ). Materials with LPE typically have κ values that ar...

SnTe is proposed to be one intriguing low-toxicity alternative to PbTe. Herein, we report the diminished lattice thermal conductivity (κL) and enhanced zT of SnTe by way of vacancy engineering. (Sn...

Pure phase NbFeSb1-xSnx (where x = 0, 0.04, 0.08, 0.12, 0.16) half-Heusler samples were prepared by direct mechanical alloying followed by spark plasma sintering. The results showed that the substitution of Sb by Sn can effectively enhance the peak figure of merit (ZT) to 0.55 at 923 K in NbFeSb0.88Sn0.12 through optimized carrier concentration. To further reduce the lattice thermal conductivity (κL), we substituted Nb by Hf to enhance the point defect scattering of phonon transport. A maximum reduction of ~80% in κL was observed in Nb0.8Hf0.2FeSb0.88Sn0.12 when compared to undoped NbFeSb at 573 K. We realized a minimum κL of ~2.96 W m−1 K−1 at 673 K and a peak ZT of ~0.82 at 973 K for Nb0.88Hf0.12FeSb0.88Sn0.12.

To recover the low-grade waste heat (300-500 K), it is of urgent importance to develop and improve the thermoelectric performance at a low-temperature region. Herein, we have realized a record high ZT value of 1.4 at 410 K and a record high average ZT value of 0.6 in the temperature interval from 300 to 400 K for Sb-doped Ag2SbxTe1-x (x = 0-0.03) compounds, which show an improvement of 180 and 120% compared to pristine Ag2Te, respectively. Sb doping increases the carrier concentration and electrical conductivity, leading to a remarkable improvement of electrical transport properties. The Ag2Sb0.015Te0.985 sample obtains the maximal power factor of 1.07 × 10-3 W m-1 K-2 at 410 K, which is increased by 80% in comparison to that of pristine Ag2Te. Moreover, as a result of the intensified alloying phonon scattering by Sb doping, Ag2Sb0.01Te0.99 possesses the minimum lattice thermal conductivity of 0.35 W m-1 K-1 at 300 K, which demonstrates a decline of 57% compared to that of pristine Ag2Te. All of these produce a great enhancement on the thermoelectric performance of Ag2Te materials, which shows great potential in the application of recycling the low-grade waste heat at a low-temperature region.

The systematic theoretical approaches and atomistic simulation programs to predict thermal properties of crystalline nanostructured materials within first-principles framework are studied here. Recent progress in computational power has enabled an accurate and reliable way to investigate nanoscale thermal transport in crystalline materials using first-principles based calculations. Extracting a large set of anharmonic force constants with low computational effort remains a big challenge in lattice dynamics and condensed-matter physics. This paper focuses on recent progress in first-principles phonon calculations for semiconductor materials and summarizes advantages and limitations of each approach and simulation programs by comparing accuracy of numerical solutions, computational load and calculating feasibility to a wide range of crystalline materials. This work also reviews and presents the coupling model of first-principles molecular dynamic (FPMD) approach that can extract anharmonic force constants directly and solution of linearized Boltzmann transport equation to predict phonon-mediated lattice thermal conductivity of crystalline materials.

The wide range of industrial applications is the main reason for an increased interest in dioxides such as HfO2. In this study, classical molecular dynamic simulations were performed to calculate the lattice thermal conductivity of the cubic phase of HfO2, over a temperature range of 100-3000 K, based on the Green-Kubo fluctuation method. In this research, the heat current autocorrelation function and lattice thermal conductivity were calculated in the a-direction. The lattice thermal conductivity of the cubic phase of HfO2 was found to be a result of three contributions. These were the optical and acoustic short-range and long-range phonon modes. Comparisons between the results of the research and experimental data when available indicate good agreement. Keywords: lattice thermal conductivity, molecular dynamics, Green-Kubo formalism, heat current autocorrelation function, hafnium dioxid

In this article, we investigate the lattice thermal conductivity in the thermoelectric Fe2VAl Heusler alloy by implementing a Green’s function approach to describe phonon-defect scattering mechanisms in the pristine and substituted compounds. Former calculations for pristine Fe2VAl largely overestimated the lattice thermal conductivity compared to the experimental value (28 W m−1 K−1). By considering a realistic concentration ( ~ 5%) of combined AlV and VAl antisite defects as an extra phonon scattering mechanism, calculated and experimental values could be reconciled. The same theoretical approach was applied to Ta- and Ta + Sn-substituted Fe2VAl. In agreement with experiments it shows that the dual Ta + Sn-substitution is more efficient in decreasing the lattice thermal conductivity of Fe2VAl than the single Ta-substitution. A strong decrease of 70% is theoretically obtained in Fe2V0.96Ta0.04Al0.96Sn0.04 which could thus lead to better global thermoelectric performances.

The superior performance of GeTe-based materials has drawn increased attention in the community of thermoelectrics. Originating mainly from the low lattice thermal conductivity (κl) caused by vast ...

Conventional PbTe-based semiconductors have been leading the developments in the thermoelectrics community due to their rich capabilities in optimizing the electronic and phonon transport properties. However, growing environmental concerns related to Pb toxicity is guiding thermoelectrics research toward the lead-free route. As an alternative analog of PbTe, SnTe has recently attracted increasing research interest for thermoelectric energy conversion. The key challenges for enhancing the thermoelectric performance of SnTe to be comparable with that of p-type PbTe include decreases in the carrier concentration, energy offset between the light valence band (L band) and heavy valence band (Σ band), and lattice thermal conductivity. In this review, the recent progresses made in SnTe alloys are first outlined. Based on the insights gained into the intrinsic nonstoichiometry as well as the electronic and phonon transport properties of SnTe materials, fundamental and successful strategies focusing on confronting the challenges faced by figure-of-merit zT enhancement in SnTe are discussed and highlighted, aiming at providing a straightforward overview on the underlying physics of these effective strategies. Eventually, future challenges and outlook are summarized for boosting advancements in environment-friendly SnTe thermoelectric materials.

Cu2SnSe3 based compounds with a diamond-like structure are promising thermoelectric materials. However, the relatively high lattice thermal conductivity limits further improvement in their thermoelectric performance. In this work, two compounds including In2Se3 and CuInSe2 are employed to alloy with Cu2SnSe3 aiming to decrease lattice thermal conductivity and their corresponding effects are compared. It is found that alloying with CuInSe2 is more beneficial to reduce lattice thermal conductivity and maintain the power factor, as evidenced by a higher quality factor B. Subsequently, both In and Ga doping is performed to regulate the carrier concentration of (Cu2SnSe3)0.80(CuInSe2)0.2. Finally, (Cu2Sn0.97Ga0.03Se3)0.80(CuInSe2)0.20 displays a decent zT of ∼0.98 at 823 K, a nearly six-fold higher value compared to that of the pristine sample. Additionally, a zTave of ∼0.35 over 300–823 K is obtained in (Cu2Sn0.97Ga0.03Se3)0.80(CuInSe2)0.20, which is among the best reported p-type Cu2SnSe3 based compounds. The result proves that alloying with CuInSe2 combined with carrier concentration optimization is a valid strategy to improve the thermoelectric performance of Cu2SnSe3 based compounds.

Thermoelectric Zintl phases have attracted increasing attention in the past few decades, with good thermoelectric performance observed in many different families. Due to their intrinsic low lattice thermal conductivity, p-type CaAl2Si2 (1-2-2)-type Zintl phases, which also exhibit relatively higher electrical transport performance, have been demonstrated to be promising thermoelectric materials for mid- to high-temperature applications. Here we investigate the thermoelectric performance of p-type SmMg2Bi2, a new member of this 1-2-2 Zintl family. Band structure calculations reveal that the calculated band gap of SmMg2Bi2 is smaller in comparison to that of other Bi-based Zintl phases, which inevitably contributes to the bipolar effect clearly observed at higher temperature. Further successful substitution of Eu and Yb is effective in suppressing the bipolar effect and ensures achievement of superior electronic performance, resulting in a peak figure of merit (ZT) of ∼0.9 at 773 K. The current work has successfully expanded the family of Bi-based p-type 1-2-2 Zintls, and could play an essential role in stimulating further investigation of other Zintl compounds.

Thermoelectrics are a promising technology for converting heat into renewable electricity. Currently, however, most of the best thermoelectrics are based on toxic and/or rare materials such as PbTe and Bi2Te3, limiting their practical applications. Transparent conducting oxides (TCOs) are well understood and widely used commercially, so if they could be made into thermoelectrics, they could be rapidly and prolifically deployed. TCOs have been tested for their thermoelectric capabilities, however their performance is far below that needed for industrial deployment. Here we use hybrid density functional theory to screen four TCOs: BaSnO3, CdO, SnO2 and ZnO for thermoelectric efficiency and analyse the limitations of TCOs as thermoelectrics. We demonstrate that the dominant factor limiting these materials is the lattice thermal conductivity, and more specifically very long phonon mean free paths up to the order 10 μm, making them strong candidates for nanostructuring to increase performance. Based on these insights we critically discuss materials design principles for increasing the ZT of the conducting oxides.

Hexagonal BC2N is a superhard material recently identified to be comparable to or even harder than cubic boron nitride (c-BN) due the full sp3 bonding character and the higher number of C–C and B–N bonds compared to C–N and B–C. Using a first-principles approach to calculate force constants and an exact numerical solution to the phonon Boltzmann equation, we show that BC2N has a high lattice thermal conductivity exceeding that of c-BN owing to the strong C–C and B–N bonds, which produce high phonon frequencies as well as high acoustic velocities. The existence of large group velocities in the optical branches is responsible for its large thermal conductivity. Its coefficient of thermal expansion (CTE) is found to match that of Si above 400 K The combination of large thermal conductivity and a good CTE match with that of Si, makes BC2N a promising material for use in thermal management and high-power electronics applications. We show that the application of compressive strain increases the thermal conductivity significantly. This enhancement results from the overall increased frequency scale with pressure, which makes acoustic and optic velocities higher, and weaker phonon–phonon scattering rates.

Half-Heusler (HH) compounds are among the most promising thermoelectric (TE) materials for large-scale applications due to their superior properties such as high power factor, excellent mechanical and thermal reliability, and non-toxicity. Their only drawback is the remaining-high lattice thermal conductivity. Various mechanisms were reported with claimed effectiveness to enhance the phonon scattering of HH compounds including grain-boundary scattering, phase separation, and electron–phonon interaction. In this work, however, we show that point-defect scattering has been the dominant mechanism for phonon scattering other than the intrinsic phonon–phonon interaction for ZrCoSb and possibly many other HH compounds. Induced by the charge-compensation effect, the formation of Co/4d Frenkel point defects is responsible for the drastic reduction of lattice thermal conductivity in ZrCoSb1−xSnx. Our work systematically depicts the phonon scattering profile of HH compounds and illuminates subsequent material optimizations.

High-performance thermoelectric devices require materials with low lattice thermal conductivity (LTC). Many strategies, such as phonon engineering, have been undertaken to reduce the LTC without simultaneously decreasing the charge-transport performance. It is a simple and effective approach to use materials with a heavy element to reduce the LTC. Here, based on first-principles calculations and Boltzmann transport equations for phonons, we found that the replacement of Zr with the heavy element Hf in ZrNCl did not reduce the LTC: instead, it increased it about four-fold at 300 K. This unusual LTC was attributed mainly to the dramatic enhancement in phonon lifetime in the Hf compound, which originated from strong interatomic bonding due to lanthanide contraction. Our findings unveil the microscopic mechanisms of the high thermal transport properties in materials with a heavy element. They also provide an alternative strategy for the design of materials with low LTC for thermoelectric applications, such as power restoration and generation.

A high conduction band degeneracy (Nv = 6) leads to an extraordinary figure of merit (zT) in n-type Mg3Sb2 thermoelectrics, while the p-type ones show a much inferior zT due to its lower Nv of only 1 owing to the large energy offset (ΔE ∼ 0.4 eV) between the two valence bands. The derivatives of Mg3Sb2, ternary AB2C2 (A = Eu, Yb, Ca, Sr, Ba; B = Mg, Zn, Cd; C = Sb, Bi) Zintls, show a similar valence band structure but with a much smaller ΔE of

Although Sb doping is regarded as the most effective method to regulate the carrier concentration within the optimum range for ZrNiSn-based half-Heusler (HH) alloys, the resulting thermal conductiv...

The figure of merit of thermoelectric materials can be increased by suppressing the lattice thermal conductivity without degrading electrical properties. Phonons are the carriers for lattice thermal conduction, and their transport can be impeded by nanostructuring, owing to the recent progress in nanotechnology. The key question for further improvement of thermoelectric materials is how to realize ultimate structure with minimum lattice thermal conductivity. From spectral viewpoint, this means to impede transport of phonons in the entire spectral domain with noticeable contribution to lattice thermal conductivity that ranges in general from subterahertz to tens of terahertz in frequency. To this end, it is essential to know how the phonon transport varies with the length scale, morphology, and composition of nanostructures, and how effects of different nanostructures can be mutually adopted in view of the spectral domain. Here we review recent advances in analyzing such spectral impedance of phonon transport on the basis of various effects including alloy scattering, boundary scattering, and particle resonance., GRAPHICAL ABSTRACT

1-2-2-type Zintl phase compound has aroused great interest for potential thermoelectric applications. However, YbMg2Sb2 is seldom studied due to the very low electrical conductivity resulting from the large difference in the electronegativity between Mg and Sb. In this paper, we adjust the covalently bonded network of MgSb by replacing part of the Mg with Zn which has the electronegativity closer to that of Sb. The decreased polarity in the anionic framework offers more free distance for electrons for the enhanced Hall mobility and electrical conductivity. Together with the increased point defect and the decreased lattice thermal conductivity by introduction of Zn, the maximum ZT value of ∼0.8 at 773 K is achieved in YbMg0.9Zn1.1Sb2 which is ∼100% enhancement compared with that of YbMg2Sb2. Keywords: Thermoelectric, Zintl phase, YbMg2Sb2, Polarity, Electronegativity

Atomic-scale defects are essential for improving thermoelectric (TE) performance of most state-of-the-art materials by simultaneously tuning the electronic and thermal properties. However, because the plural atomic-scale defects are generally inherent and disordered in nanostructured TE materials, their complexity and ambiguity on determining TE performance remain a challenge to be solved. Furthermore, the thermal stability of atomic-scale defects in nanostructured TE materials has not been studied much so far. Herein, we report that the atomic-scale defect disorders are indispensable for high TE performance of nanostructured Ti1–xHfxNiSn1–ySby half-Heusler alloys, but gradually degraded at over 773 K, deteriorating the TE performance. It is found from the thermal annealing of nanostructured Ti0.5Hf0.5NiSn0.98Sb0.02 alloys that the annihilation of Ti,Hf/Sn antisite defects primarily reduces atomic-scale defect disorders and largely contributes to the increase of lattice thermal conductivity. Moreover, it is verified that the Ni interstitial defects mainly dominate the electronic transport properties, leading to the enhancement of power factor. Direct atomic structure observations clearly demonstrate the inherent Ni interstitial defects and the thermal vulnerability of Ti,Hf/Sn antisite defects. These results provide an important guide for the application of half-Heusler alloys with highly disordered atomic-scale defects.

In recent years, the layered semiconductor tin selenide (SnSe) has been of great interest in the thermoelectric field because of its remarkable thermoelectric potential. Here, the as-grown Sn0.98Se...

The ternary chalcopyrite AgInSe2 has emerged as a promising n-type thermoelectric material with ultralow lattice thermal conductivity. We report the thermoelectric transport properties of sodium-do...

High purity CoSb3, Ni0.06Co0.94Sb3 and In0.13Co4Sb12 were synthesized from oxides by magnesioreduction. This novel synthesis route to CoSb3-based skutterudites directly yields highly crystalline powders with submicronic grain size. Densified mesostructured pellets with an average grain size ranging between 550 and 800 nm were obtained by spark plasma sintering. The strong phonon scattering induced by the mesostructuration leads to a lattice thermal conductivity reduction up to 25% for CoSb3 and Ni0.06Co0.94Sb3 at 300 K without significantly degrading the electronic properties. Consequently, maximum ZT figures-of-merit of 0.09, 0.60 and 0.75 are found for CoSb3, Ni0.06Co0.94Sb3 and In0.13Co4Sb12, respectively, showing the ability of this scalable process to reach the best performances reported in literature for these compositions at moderate temperature and annealing duration.

Elemental tellurium exhibits a promising thermoelectric performance, largely due to the optimization of the carrier concentration stemming from effective chemical doping. In this study, we demonstr...

As an environment-friendly alternative to traditional PbTe, many attempts have recently been made to improve thermoelectric SnTe. Effective strategies are mainly focused on valence band convergence, nanostructuring, interstitial defects, and alloying solubility. In particular, alloying SnTe with CdTe/GeTe triggers an inherent decline of valence band offset effectively owing to a high solubility of ∼20% of CdTe. However, to what level an additional element doping in low-solubility SnTe-CdTe alloys can play a role in enhancing the thermoelectric performance still remains a mystery. Here, a new strategy is shown that unexpected Bi doping, by alloying with only ∼3% CdTe, induces a significant enhancement of the thermoelectric figure of merit ZT to be ∼240% (ZT up to ∼1.3) at 838 K, which is mainly determined by the dramatically reduced lattice thermal conductivity above 800 K deriving from the exotic Bi doping and Cu-interstitial defects. More interestingly, combining experimental and theoretical evidences, the Bi-doping-driven band convergence is also beneficial to the improvement of thermoelectric performance below 800 K. The present findings demonstrate the extraordinary role of Bi for advancing the thermoelectric performance in SnTe alloys.

Although introducing more fillers in nanocages is beneficial to gain low lattice thermal conductivity within filling fraction limit, accompanying high electronic thermal conductivity usually results in an unsatisfactory figure of merit

SnTe has been regarded as an environment-friendly alternative of PbTe thermoelectrics, although its performance is limited by its high thermal conductivity, partly owing to its high carrier concent...

We investigated the lattice thermal conductivity (LTC) of a subset of polymer crystals from the polymer genome library to explore high LTC polymer systems. We employed a first-principles approach t...

In this study, we investigated the effect of lattice defects comprising vacancies and boundaries on the lattice thermal conductivity (LTC), κp, of suspended molybdenum disulfide monolayers (MLs) over a wide temperature range (1

Al doped PbTe-PbSe alloys were successfully prepared with high pressure synthesis followed by spark plasma sintering. The incorporation of Se shows a dual effect on the system. Firstly, the carrier concentration can be further modified with varying Se content, on the basis of Al doping. Secondly, the lattice thermal conductivity can be greatly suppressed due to the alloying effect. Beneficial from this, the average ZT of AlxPbTe1-ySey samples are remarkably enhanced compared with the unalloyed ones. The highest average ZT of 0.82 is achieved in Al0.02PbTe0.75Se0.25, which is 60% higher than that of Al0.02PbTe. Combining strategies of dynamic doping and/or hierarchical phonon scattering, the thermal performance of n-type PbTe-based materials may be further enhanced.

p-type Bi0.46Sb1.54Te3 samples containing nanoprecipitates are prepared by mechanical alloying (MA) and spark plasma sintering (SPS) technique. The thermoelectric performance of Bi0.46Sb1.54Te3 is improved by the energy filtering effect induced by nanoprecipitates, leading to a high ZT value of 1.18 at 325 K. To further improve the thermoelectric performance of Bi0.46Sb1.54Te3, SiC nanoparticles are dispersed into Bi0.46Sb1.54Te3 matrix. The addition of SiC simultaneously increases the electrical conductivity and the Seebeck coefficient. Meanwhile, it also decreases the lattice thermal conductivity from 0.38 to 0.33 Wm−1K−1 for the 0.2 wt% SiC sample. Consequently, a maximum ZT value of 1.45 at 325 K is obtained for Bi0.46Sb1.54Te3 with the addition of 0.2 wt% SiC composites, which increases about 23% than the pristine sample.

We report a facile and efficient way to enhance and modulate thermoelectric performance by incorporating chemically synthesized Cu2Te nanoparticles on p-type Bi0.5Sb1.5Te3 matrix. By varying the amount of Cu2Te nanoparticles, the temperature of maximum thermoelectric performance shifted systematically from room temperature to 425 K. The highest figure-of-merit value, 1.1, was achieved at 377 K by incorporating 0.1 wt% Cu2Te nanoparticles in Bi0.5Sb1.5Te3 matrix, which is due to enhancement in power factor and reduction in lattice thermal conductivity. The results demonstrate that Cu2Te incorporation could be an effective strategy for Bi-Te based thermoelectric power generation.

SnSe-based materials possess ultrahigh thermoelectric efficiency and show great potential in next-generation thermoelectric devices. The excellent thermoelectric performance of SnSe has been attrib...

Six new quaternary chalcogenides belonging to the pavonite sulfosalt mineral family with the general formula Mn+1(Bi/Sb)2Qn+5 (n = 2–7) were synthesized by direct reactions of the elements at high ...

In this work, we reported the thermoelectric performance of Sb doped n-type PbS can be improved through introducing different types of Cu inclusions (counter-doping, extra-adding and both of them). Firstly, Cu was selected to substitute Pb sites as counter-doping to tune the carrier density, resulting in maintaining power factor but a decreasing total thermal conductivity, thus in a maximum ZT (ZTmax) ∼ 0.96 at 923 K in Pb0.975Sb0.02Cu0.005S. Then, we introduced extra Cu in n-type PbS to form interstitials to further reduce the lattice thermal conductivity to ∼0.77 W m − 1 K − 1 , and the ZTmax was further enhanced to ∼1.06 at 923 K in Pb0.98Sb0.02S-0.02Cu. Finally, we combined both types of Cu (counter-doping and extra-adding) into n-type PbS, the power factor experiences slight reduction meanwhile the minimum lattice thermal conductivity can be reduced as low as ∼ 0.57 W m − 1 K − 1 at 923 K. Combining excellent power factor and dramatically reduced lattice thermal conductivity, we obtained a ZTmax ∼1.23 at 923 K and the ZTave ∼0.62 at 300–923 K in Pb0.95Sb0.02Cu0.03S-0.03Cu. This work provides a new idea to improve the thermoelectric performance in n-type PbS, indicating that PbS is one robust alternative of PbTe.

Recently, polycrystalline argyrodite Ag8SnSe6 has shown promising thermoelectric performance, which largely relies on the ultralow lattice thermal conductivity. However, the thermoelectric properti...

Due to their thermoelectric properties, intermetallic clathrates are technologically highly interesting materials. Especially their strongly reduced lattice thermal conductivity has been largely investigated and strongly debated. Although density-functional-theory-based lattice dynamics calculations have helped clarify the thermal transport in clathrates, significant discrepancies remain between experiment and theory, especially in Ge-based clathrates. In this work, we show that the recently released meta-generalized-gradient approximation functional SCAN (strongly constrained and appropriately normed) is able to overcome these issues and provide a much improved agreement between the experimental and the theoretical phonon spectra, thus enabling quantitative predictions of the clathrate phases with a high potential for thermoelectric applications.

Compositional tuning is one of the important approaches to enhance the electronic and thermal transport properties of thermoelectric materials since it can generate point defects as well as control the phase evolution behavior. Herein, we investigated the Ti addition effect on the grain growth during melt spinning and thermoelectric transport properties of Hf0.5Zr0.5NiSn0.98Sb0.02 half-Heusler compound. The characteristic grain size of melt-spun ribbons was reduced by Ti addition, and very low lattice thermal conductivity lower than 0.27 W m−1 K−1 was obtained within the whole measured temperature range (300–800 K) due to the intensified point defect (substituted Ti) and grain boundary (reduced grain size) phonon scattering. Due to this synergetic effect on the thermal transport properties, a maximum thermoelectric figure of merit, zT, of 0.47 was obtained at 800 K in (Hf0.5Zr0.5)0.8Ti0.2NiSn0.98Sb0.02.

The ternary Cu3SbSe4 thermoelectric material with diamond-like structure exhibit good thermoelectric performance in the middle temperature region. In this study, the Cu3−xNixSbSe4 (x = 0–0.03) materials were fabricated by melting-ball milling-hot pressing process. The influences of grain size and compositional gradient on the microstructure and thermoelectric properties of Cu3−xNixSbSe4 were evaluated. It is found that the electrical conductivity of Cu2.97Ni0.03SbSe4 was about 33% higher than that of Cu3SbSe4 sample, and the lattice thermal conductivity was reduced from 3.3 Wm−1K−1 to 2.4 Wm−1K−1 at room temperature due to the grain refinement and more VSe defects. The maximum zT value for the Cu2.97Ni0.03SbSe4 sample was 0.62 at 650 K.

In this paper, the thermoelectric properties of p-type and n-type GeSe are studied systematically by using first principles and Boltzmann transport theory. The calculation includes electronic structure, electron relaxation time, lattice thermal conductivity and thermoelectric transport properties. The results show that GeSe is an indirect band gap semiconductor with band gap 1.34 eV. Though p-type GeSe has a high density of states near Fermi level, the electronic conductivity is relative low because there is no carrier transport pathway along the a -axis direction. For n-type GeSe, a charge density channel is formed near conduction band minimum, which improves the electrical conductivity of n-type GeSe along the a -axis direction. At 700 K, the optimal ZT value reaches 2.5 at 4 × 10 19 cm −3 for n-type GeSe, while that is 0.6 at 1 × 10 20 cm −3 for p-type GeSe. The results show n-type GeSe has better thermoelectric properties than p-type GeSe, indicating that n-type GeSe is a promising thermoelectric material in middle temperature.

Lattice thermal conductivity (${\ensuremath{\kappa}}_{\mathrm{lat}}$) of $\mathrm{Mg}\mathrm{Si}{\mathrm{O}}_{3}$ postperovskite (MgPPv) under the Earth's lower mantle high pressure-temperature conditions is studied using the phonon quasiparticle approach by combing ab initio molecular dynamics and lattice dynamics simulations. Phonon lifetimes are extracted from the phonon quasiparticle calculations, and the phonon group velocities are computed from the anharmonic phonon dispersions, which, in principle, capture full anharmonicity. It is found that throughout the lowermost mantle, including the D'' region, ${\ensuremath{\kappa}}_{\mathrm{lat}}$ of MgPPv is \ensuremath{\sim}25% larger than that of $\mathrm{Mg}\mathrm{Si}{\mathrm{O}}_{3}$ perovskite (MgPv), mainly due to MgPPv's higher phonon velocities. Such a difference in phonon velocities between the two phases originates in the MgPPv's relatively smaller primitive cell. Systematic results of temperature and pressure dependences of both MgPPv's and MgPv's ${\ensuremath{\kappa}}_{\mathrm{lat}}$ are demonstrated.

Thermoelectric materials have been expected as a critical underlying technology for developing an autonomous power generation system driven at near room temperature. For this sake, Fe3Al2Si3 intermetallic compound is a promising candidate, though its high lattice thermal conductivity is a bottleneck toward practical applications. Herein, we have performed the first-principles calculations to clarify the microscopic mechanism of thermal transport and establish effective ways to reduce the lattice thermal conductivity of Fe3Al2Si3. Our calculations show that the lowest-lying optical mode has a significant contribution from Al atom vibration. It should correspond to large thermal displacements Al atoms. However, these behaviors do not directly cause an increase of the 3-phonon scattering rate. The calculated lattice thermal conductivity shows a typical temperature dependence and moderate magnitude. From the calculated thermal conductivity spectrum and cumulative thermal conductivity, we can see that there is much room to reduce the lattice thermal conductivity. We can expect that heavy-element doping on Al site and controlling fine microstructure are effective strategies to decrease the lattice thermal conductivity. This work suggests useful information to manipulate the thermal transport of Fe3Al2Si3, which will make this material closer to practical use.