Thermoelectric Applications Research Articles

Potential improvement in thermoelectric properties of SnTe polycrystals via anionic and cationic substitution

Heat is produced by all machinery, including microprocessors and jet engines, as well as by industrial processes that produce goods from steel to food. There is still a strong desire for alternative energy sources in this day of ecologically conscious and sustainable energy needs. The recovery of heat from waste heat into beneficial electrical energy provides a simple energy source with enormous potential. Thermoelectrics is one of the popular technologies, which can convert heat into electricity, making them useful for power generation. Tin telluride (SnTe), a significant type of newly developed thermoelectric material, has drawn a lot of attention due to its low toxicity and environmentally friendly characteristics. Here, we synthesize Bi/Se co-doped SnTe (Sn1-xBixTe0.97Se0.03 (x = 0, 0.02, 0.04, 0.06)) samples by employing the solid-state metathesis route. The results of this work suggest that the combined action of cationic and anionic substitution of Bi and Se to SnTe matrix could potentially modify the microstructure and band structure of SnTe, thereby effectively improving its electronic, mechanical, and thermal transport properties. In line with the experimental findings, the samples show degenerate semiconducting electronic transport behaviour throughout the temperature range. The maximum Seebeck coefficient is found to be ∼84 μV/K and the total thermal conductivity is reduced to 1.6 W/mK at 573 K in a 6 % Bi-doped sample, which is 2.2 times less than the pristine sample. The Sn0.94Bi0.06Te0.97Se0.03 sample has a maximum ZT of approximately 0.23 at 573 K, which is three times higher than the pristine sample because of the combined regulation of cation-anion co-doping and an elevated power factor of 936 μW/K2m in Sn0.96Bi0.04Te0.97Se0.03 sample at 573 K, which is 1.82 times higher than that of pristine SnTe. Considering these findings, it appears that Bi-Se co-doped SnTe is a promising material for thermoelectric applications.

Enhancement in power factor through rare-earth samarium doping in Cu2SnSe3 system

Cu2SnSe3 has drawn enough attention as a potential thermoelectric material due to its unique electronic and thermal properties. We present the impact of Sm doping on the Cu2SnSe3 system’s Sn site. The polycrystalline samples of Cu2Sn1-x Sm x Se3 (0 ≤ x ≤ 0.08) were prepared using the solid-state reaction technique followed by conventional sintering. The crystal structure was characterized using XRD and the results reveal that the samples have a diamond cubic structure with a space group of F4̄3m. Scanning Electron Microscopy (SEM) analysis indicates a uniform surface homogeneity within the sample. Furthermore, the introduction of Sm causes a reduction in porosity. The electrical transport characteristics were studied in the mid temperature range of 300–650 K. The Seebeck coefficient of all the samples were found to be positive within the temperature range under study, suggesting that holes constitute the majority charge carriers. This is also confirmed by the Hall measurements as the carrier concentration was positive for all the samples. The inclusion of Sm has led to a reduction of electrical resistivity and Seebeck coefficient and hence power factor of ~539 μW mK−2 for x = 0.08 at 630 K which is ten times greater as compared to x = 0 whose power factor is ~56 μW mK−2 at 630 K is achieved which makes it suitable for thermoelectric applications.

Simultaneous Characterization of In-Plane and Cross-Plane Resistivities in Highly Anisotropic 2D Layered Heterostructures.

Understanding and characterizing the intrinsic properties of charge carrier transport across the interfaces in van der Waals heterostructures is critical to their applications in modern electronics, thermoelectrics, and optoelectronics. However, there are very few published cross-plane resistivity measurements of thin samples because these inherently 2-probe measurements must be corrected for contact and lead resistances. Here, we present a method to extract contact resistances and metal lead resistances by fitting the width dependence of the contact end voltages of top and bottom electrodes of different contact widths to a model based on current crowding. These contributions are then subtracted from the total 2-probe cross-plane resistance to obtain the cross-plane resistance of the material itself without needing multiple devices and/or etching steps. This approach was used to measure cross-plane resistivities of a (PbSe)1(VSe2)1 heterostructure containing alternating layers of PbSe and VSe2 with random in-plane rotational disorder. Several samples measured exhibited a 4 order of magnitude difference between cross-plane and in-plane resistivities over the 6-300 K temperature range. We also reported the observation of charge density wave transition in the cross-plane transport of the (PbSe)1(VSe2)1 heterostructure. The device fabrication process is fully liftoff compatible, and the method developed enables the straightforward measurement of the resistivity anisotropy of most thin film materials with nm thicknesses.

Hydrogel‐Based Functional Materials for Thermoelectric Applications: Progress and Perspectives

AbstractHydrogels are renowned for their complex structures and unique physicochemical properties, establishing them as key materials in bioenergy harvesting applications. They are used in various applications, including triboelectric nanogenerators, piezoelectric, hydraulic, thermoelectric, and biofuel cells. Among these, hydrogels as key materials for thermoelectric applications represent a technology capable of continuously converting biological energy (thermal energy) into electrical energy. This technology shows great potential and commercial value in body monitoring, energy storage, and human‐machine interaction applications. Given its rapid development, a timely review focusing on the research progress of hydrogels and their composites in thermoelectric technology is presented. This review discusses various types of hydrogels used for thermoelectric power generation and refrigeration, their unique properties, strategies for enhancing their thermoelectric performance, and their applications in the field. Finally, the remaining challenges and feasible strategies are identified for improving the efficiency, stability, application range, and system‐level integration of next‐generation hydrogels for thermoelectric applications.

Exploring Doping Mechanisms and Modulating Carrier Concentration in Copper Iodide: Applications in Thermoelectric Materials.

Due to its small hole-effective mass, flexibility, and transparency, copper iodide (CuI) has emerged as a promising p-type alternative to the predominantly used n-type metal oxide semiconductors. However, the lack of effective doping methods hinders the utility of CuI in various applications. Sulfur (S)-doping through liquid iodination is previously reported to significantly enhance electrical conductivity up to 511Scm-1. In this paper, the underlying doping mechanism with various S-dopants is explored, and suggested a method for controlling electrical conductivity, which is important to various applications, especially thermoelectric (TE) materials. Subsequently, electric and TE properties are systematically controlled by adjusting the carrier concentration from 3.0×1019 to 4.5×1020cm-3, and accurately measured thermal conductivity with respect to carrier concentration and film thickness. Sulfur-doped CuI (CuI:S) thin films exhibited a maximum power factor of 5.76µWcm-1K-2 at a carrier concentration of 1.3×1020cm-3, and a TE figure of merit (ZT) of 0.25. Furthermore, a transparent and flexible TE power generator is developed, with an impressive output power density of 43nWcm-2 at a temperature differential of 30K. Mechanical durability tests validated the potential of CuI:S films in transparent and flexible TE applications.

Thermoelectric hydrogels for self-powered wearable biosensing

Although the flourishing of the Internet of Things and artificial intelligence has accelerated the development of wearable smart bioelectronics, heavy reliance on external power remains a problem that needs to be solved. Thermoelectric materials have emerged as a promising solution, efficiently converting body heat into electrical energy to provide a stable and unrestricted power supply for wearables. Moreover, in the field of wearable thermoelectric biosensing, where flexibility is highly demanded, hydrogels with excellent electrical conductivity, flexibility and biocompatibility through structural and compositional optimization have become ideal materials for constructing biosensors and meet the diverse application needs of wearable bioelectronics. This article systematically reviews the latest research progress on thermoelectric gels for self-powered wearable biosensing, including the principles of thermoelectric operation, as well as the preparation, design, and application of thermoelectric hydrogels. The current state of thermoelectric gel-based wearable applications in the fields of temperature sensing, strain sensing, temperature-strain synergistic sensing, respiratory monitoring, and sweat analysis are displayed in the article. Finally, the paper summarizes the current challenges and prospects of thermoelectric gels in self-powered wearable bioelectronics, encouraging the rapid application and realization of thermoelectric gel-based smart wearables.

Advanced GeSe-based thermoelectric materials: Progress and future challenge

GeSe, composed of ecofriendly and earth-abundant elements, presents a promising alternative to conventional toxic lead-chalcogenides and earth-scarce tellurides as mid-temperature thermoelectric applications. This review comprehensively examines recent advancements in GeSe-based thermoelectric materials, focusing on their crystal structure, chemical bond, phase transition, and the correlations between chemical bonding mechanism and crystal structure. Additionally, the band structure and phonon dispersion of these materials are also explored. These unique features of GeSe provide diverse avenues for tuning the transport properties of both electrons and phonons. To optimize electrical transport properties, the strategies of carrier concentration engineering, multi-valence band convergence, and band degeneracy established on the phase modulation are underscored. To reduce the lattice thermal conductivity, emphasis is placed on intrinsic weak chemical bonds and anharmonicity related to chemical bonding mechanisms. Furthermore, extra-phonon scattering mechanisms, such as the point defects, ferroelectric domains, boundaries, nano-precipitates, and the phonon mismatch originating from the composite engineering, are highlighted. Additionally, an analysis of mechanical properties is performed to assess the long-term service of thermoelectric devices based on GeSe-based compounds, and correspondingly, the theoretical energy-conversion efficiency is discussed based on the present zT values of GeSe. This review provides an in-depth insight into GeSe by retrospectively examining the development process and proposing future research directions, which could accelerate the exploitation of GeSe and elucidate the development of broader thermoelectric materials.

Enhancement of thermoelectric performance by Ag/Bi/Fe co-doping into Cu3SbSe4 ceramics for green thermoelectric applications

Cu3SbSe4 is recognized for its abundant elemental availability, cost-effectiveness, and non-toxic properties, making it a promising candidate for thermoelectric applications at medium temperatures. This study explored the preparation of Bi/Fe, Ag/Fe, and Ag/Bi double-doped Cu3SbSe4 ceramics using vacuum melting and cold isostatic pressing techniques. The focus was on examining the influence of these dopants on the microstructural and thermoelectric performances of Cu3SbSe4. The analysis revealed the presence of Cu3SbSe4 and Cu2−xSe phases in the doped samples. Double doping optimized the carrier concentration, increased the effective mass, and significantly enhanced the electrical conductivity from 12.45 to 64.01 S cm−1. Notably, the power factor of the Cu2.85Ag0.15Sb0.985Bi0.015Se4 sample reached 649.1 μWm−1K−2 at 573 K. Furthermore, the thermal conductivity was significantly reduced to 0.73 W/mK. The maximum ZT value of the Cu2.85Ag0.15Sb0.985Bi0.015Se4 sample was 0.47 at 573 K. These breakthrough results demonstrate that dual doping markedly enhances the thermoelectric properties of the Cu3SbSe4 system.

Computational investigation of electronic, thermoelectric, and optical properties in Cs2Li[formula omitted](X = Br, I) for energy harvesting applications

The remarkable potential of double perovskite materials, characterized by lead-free, non-toxic attributes and robust dynamical stability, positions them as highly promising candidates for both thermoelectric and optoelectronic applications. In light of this, a comprehensive investigation is undertaken through density functional theory to thoroughly explore the optoelectronic and transport characteristics of Cs2LiBiX6 (X = Br, I) double perovskite materials. To ascertain dynamic stability, phonon dispersion band structures are computed, and the structural stability is evaluated through the tolerance factor. The resulting band structures reveal narrow band gaps of 3.45 eV and 1.79 eV for the Br and Indium-based DPs, respectively. These narrow band gaps hold significant importance for applications such as ultraviolet detectors and other optoelectronic devices that function in the visible and UV-light spectrum. Notably, absorption peaks of maximal intensity emerge at 5.1 eV (76 nm) and 4.0 eV (67 nm) for the Br and Indium-based double perovskites, respectively. Furthermore, a comprehensive analysis of thermoelectric behavior is conducted, encompassing the figure of merit, power factor, Seebeck coefficient, and the ratio of electrical to thermal conductivity across a temperature range of 50–800 K. The exceptionally low lattice vibration values, coupled with a substantial enhancement in the thermoelectric figure of merit (ZT), notably underscore their significance for advanced thermoelectric generator applications.

Few-layer Bi2O2Se: a promising candidate for high-performance near-room-temperature thermoelectric applications

Advancements in high-temperature thermoelectric (TE) materials have been substantial, yet identifying promising near-room-temperature candidates for efficient power generation from low-grade waste heat or TE cooling applications has become critical but proven exceedingly challenging. Bismuth oxyselenide (Bi2O2Se) emerges as an ideal candidate for near-room-temperature energy harvesting due to its low thermal conductivity, high carrier mobility and remarkable air-stability. In this study, the TE properties of few-layer Bi2O2Se over a wide temperature range (20-380 K) are investigated, where a charge transport mechanism transitioning from polar optical phonon to piezoelectric scattering at 140 K is observed. Moreover, the Seebeck coefficient (S) increases with temperature up to 280 K then stabilizes at∼-200μV K-1through 380 K. Bi2O2Se demonstrates high mobility (450 cm2V-1s-1) within the optimum power factor (PF) window, despite itsT-1.25dependence. The high mobility compensates the minor reduction in carrier densityn2Dhence contributes to maintain a robust electrical conductivity∼3 × 104S m-1. This results in a remarkable PF of 860μW m-1K-2at 280 K without the necessity for gating (Vg= 0 V), reflecting the innate performance of the as-grown material. These results underscore the considerable promise of Bi2O2Se for room temperature TE applications.

Size and surface-dependent phase transition temperature in Cu2Se nanobridges

The critical phase transition temperature (Tc) of Cu2Se thermoelectric nanomaterials has been a focal point of extensive research, yet the quantification of surface energy on Tc is frequently ignored. In this paper, we systematically investigate the impact of both the width/thickness and surface configuration of Cu2Se nanobridges (NBs) on Tc. We find that the Tc decreases with size reduction, which becomes particularly accelerated when the size decreases to a few nanometers. Additionally, the NBs with higher energy surfaces exhibit lower Tc. Then we propose an optimized thermodynamic model to quantify the combined effect of size and surface energy on Tc in Cu2Se NBs, which provides an approach to predict Tc in Cu2Se and other thermoelectric nanomaterials. Our study facilitates the understanding of the dependence of Tc on size and surface in Cu2Se, with an eye towards the stable room temperature thermoelectric applications of Cu2Se nanomaterials.

Engineered Two-Dimensional Transition Metal Dichalcogenides for Energy Conversion and Storage.

Designing efficient and cost-effective materials is pivotal to solving the key scientific and technological challenges at the interface of energy, environment, and sustainability for achieving NetZero. Two-dimensional transition metal dichalcogenides (2D TMDs) represent a unique class of materials that have catered to a myriad of energy conversion and storage (ECS) applications. Their uniqueness arises from their ultra-thin nature, high fractions of atoms residing on surfaces, rich chemical compositions featuring diverse metals and chalcogens, and remarkable tunability across multiple length scales. Specifically, the rich electronic/electrical, optical, and thermal properties of 2D TMDs have been widely exploited for electrochemical energy conversion (e.g., electrocatalytic water splitting), and storage (e.g., anodes in alkali ion batteries and supercapacitors), photocatalysis, photovoltaic devices, and thermoelectric applications. Furthermore, their properties and performances can be greatly boosted by judicious structural and chemical tuning through phase, size, composition, defect, dopant, topological, and heterostructure engineering. The challenge, however, is to design and control such engineering levers, optimally and specifically, to maximize performance outcomes for targeted applications. In this review we discuss, highlight, and provide insights on the significant advancements and ongoing research directions in the design and engineering approaches of 2D TMDs for improving their performance and potential in ECS applications.

Solution Synthesis and Diffusion-Mediated Formation Pathway of NbTe4 Particles.

NbTe4 is an important material because of its fundamental low-temperature electronic behavior and its potential interest for thermoelectric, catalytic, and phase-change applications, especially as nano- and microscale particles. As a tellurium-rich group V transition metal telluride, bulk NbTe4 is typically synthesized through high-temperature solid-state or metal flux reactions and NbTe4 films can be made by sputtering and annealing, but NbTe4 is generally not amenable to the lower-temperature solution-based syntheses that yield small particles. Here, we demonstrate a solvothermal route to NbTe4 particles that is based on mainstream colloidal nanoparticle synthesis. We find that the reaction proceeds in situ through a multistep pathway that begins by first forming elemental tellurium needles. NbTe4 then deposits on the surface of the tellurium needles through a diffusion-based process. Time-point studies throughout the reaction reveal that crystallographic relationships between Te and NbTe4 define how the diffusion-based reaction proceeds and help to rationalize the morphology of the resulting NbTe4 particles. As synthesized, NbTe4 particles exhibit a surface consisting of predominantly Nb-Te and reduced NbOx species, but after storage, surface oxidation transforms these species to primarily Nb2O5 and TeO2, while the NbTe4 remains unchanged. These synthetic capabilities and reaction pathway insights for NbTe4, made using a solvothermal method, will help to advance future studies on the properties and applications of this and related tellurides.

Effective Out‐Of‐Plane Thermal Conductivity of Silicene by Optothermal Raman Spectroscopy

AbstractSilicene has recently been revisited as a 2D material with potential thermoelectric applications. Here, the thermal properties of supported silicene are determined by optothermal Raman spectroscopy. Single and multilayer silicene is grown either directly on silver (Ag) substrates or on an intermediate tin (Sn) monolayer, introduced to reduce the influence of the substrate on the physical properties of silicene. Experimental values of an effective cross‐plane thermal conductivity of 0.5 W/mK are obtained for silicene on Ag and 0.3 W/mK for silicene on stanene‐Ag. The values of the interfacial thermal conductance, on the other hand, are 0.3 and 0.5 GW/m2K, respectively. Heterostack engineering is confirmed as a versatile strategy for extracting relevant physical parameters in silicene and for modulating the thermal response in the 2D limit.

Properties of bismuth based Bi2A3 (A = S, Se, Te) chalcogenides for optoelectronic and thermoelectric applications

Structural, electronic, optical, mechanical, thermoelectric and dielectric properties of binary Bi2A3 (A = S, Se, Te) chalcogenide semiconductors are studied by first-principles approach. Bismuth sulfide (Bi2S3) is found to be structurally stable in orthorhombic structure while bismuth selenide (Bi2Se3) and bismuth telluride (Bi2Te3) are stable in trigonal structure. Calculated mechanical properties reveal that all three Bi2A3 (A = S, Se, Te) compounds fulfil the mechanical stability criteria. Band structure calculations reveal that the Bi2S3 exhibits direct optical band gap (Eg = 1. 58 eV) which lies in the near-infrared (NIR) region, while the calculated Eg of Bi2Se3 and Bi2Te3 are found to be 0.53 eV and 0.35 eV, respectively lying in the far-infrared region. For Bi2S3 and Bi2Se3 compounds, the calculated dielectric properties show strong anisotropic behavior, while negligible anisotropic dielectric behavior is observed for Bi2Te3. Calculated optical properties show that all three Bi2A3 compounds possess high absorption coefficient (> 104 cm−1). For all three Bi2A3 (A = S, Se, Te) compounds, the calculated optical conductivity show prominent peak corresponding to the occurrence of optical conduction at energies 3.36 eV, 2.65 eV and 2.02 eV respectively. Calculated optical results support the results deduced from band structures and density of states spectra. Optical properties and dielectric behavior suggest that the Bi2S3 compound has suitable band gap and has potential to use for photovoltaic applications while Bi2A3 (A = Se, Te) compounds could be used in infrared detectors and other optical devices. Calculated thermal properties reveal that the Bi2A3 (A = S, Se, Te) chalcogenides could be potential materials for thermoelectric applications.

Enhancing solar thermoelectric power generation with supercritical CO2 cooling: Hydraulic, thermal, and exergy analysis

This research investigates the dynamic behavior and impact of various factors on the hydraulic, thermal, and exergetic characteristics of a solar-based thermoelectric device using a pin–fin heatsink cooled by supercritical CO2. A comprehensive numerical model analyzes the heat dissipation and performance of the power generator, integrating a thermoelectric generator and a pin–fin heatsink with various pin shapes. Key geometric and operational parameters, such as the height of PN (P-type and N-type semiconductor) legs of the TEG, the number of thermocouples, operating pressure, Reynolds number, and CO2 temperature, are examined for a comprehensive performance assessment. The study highlights the superior performance of CO2 coolant over traditional water-cooling system. Near the critical temperature of CO2, enhanced heat transfer significantly boosts power output, conversion efficiency, and exergetic efficiency. For example, at 8 MPa, the TEG’s (thermoelectric generator) power output increases from 1.31 mW at 295 K to 2.35 mW at 310 K. Comparisons reveal that while water coolant lowers the cold side temperature more effectively, it results in reduced power output due to decreased temperature differentials and increased pressure loss. Conversely, CO2 coolant maintains higher cold side temperatures while having advantages in power output. At 315 K, the cold side temperature with water is 315.7 K compared to 346.7 K with CO2. Increasing the number of thermocouples from 18 to 32 for a leg height of 1 mm leads to an approximate 102.3 % increase in voltage. Raising the PN leg height from 1 mm to 2 mm for an NTC of 50 results in a nearly 99.8 % increase in voltage. Lozenge-shaped fin produces a peak power output of 2.73 mW, while square fin generates 2.62 mW. This research underscores CO2’s potential as a high-performance coolant in solar thermoelectric applications, offering insights into optimizing system design for maximum efficiency.

Exploring the impact of hydrostatic pressure on the essential physical properties of BaTiO3 perovskite: A first principles quantum investigation and prospects for optoelectronic and thermoelectric applications

This research investigates how externally applied hydrostatic pressure ranging from 0 to 100 GPa impacts the cubic BaTiO3 perovskite compound through computational simulations. The results reveal that the bandgap value increases and shifts in the visible spectrum by applying pressures from 0 to 100 GPa. The absence of negative frequencies in the phonon dispersion confirms the dynamic stability of cubic BaTiO3 compound. The BaTiO3 maintains its cubic phase and exhibits remarkable mechanical stability with ductile behavior when subjected to high pressures. The optical properties of cubic BaTiO3 compound have been meticulously investigated utilizing complex dielectric function, complex refractive index, optical reflectivity, absorption coefficient, optical conductivity, and energy loss function across the energy spectrum up to 50 eV. The study identifies maximum absorption peaks in the UV region. So, cubic BaTiO3 compound under the effect of different pressures is suitable for broadly tunable phosphor material for energy-efficient w-LEDs, optoelectronic and thermoelectric applications.

Tailored thermoelectric performance of poly(phenylene butadiynylene)s/carbon nanotubes nanocomposites towards wearable thermoelectric generator application

In this study, two conjugated polymers (CPs) featuring poly(phenylene butadiynylene) (PPB) were meticulously synthesized and composited with single-walled carbon nanotubes (SWCNTs) to investigate their thermoelectric properties and fabricate wearable thermoelectric generators (TEGs). These CPs, designated as P1 and P2, were tailored with distinct side chain configurations by incorporating 2-butyloctyloxy and 6-(methyldioctylsilyl)hexyloxy groups, respectively. Notably, P2, characterized by longer side chains with branchpoints farther from the backbone, exhibited planar backbone structure and enhanced solubility, consequently engendering stronger π–π interaction with SWCNTs and facilitating the disperse of SWCNTs through polymer wrapping at bundle surface. Such characteristics therefore contributed to the superior thermoelectric performances of the P2/SWCNTs nanocomposite, yielding a higher power factor (PF) of 216.5 μW m−1 K−2 for the spin-coated film. Furthermore, the corresponding wearable TEGs, which were constructed through spray-coating with 14 legs, resulted in an output power of approximately 49.6 nW under a temperature difference of 25 K, exhibiting successful harvesting of waste heat. Further applications also demonstrated operational efficacy under diverse conditions. These findings not only underscored the significance of side chain engineering in tailoring the thermoelectric properties of CP/SWCNTs nanocomposites but also demonstrated the feasibility of fabricating high-performance wearable thermoelectric devices applicable in versatile contexts.

Record High Thermoelectric Figure of Merit of a III-V Semiconductor InGaSb by Defects Engineering via the Addition of Excess Constituent Elements.

Materials with enhanced electron and reduced phonon transport properties are preferred for thermoelectric applications. The defect engineering process can optimize the interrelated electron and phonon transport properties to enhance thermoelectric performance. As the influence of various crystalline defects on the functional properties of materials is diverse, it is crucial to scale, optimize, and understand them experimentally. With this perspective, crystalline defects in InGaSb ternary alloys were engineered and their influence on the thermoelectric properties was studied experimentally. Crystalline defects such as point defects, dislocations, and compositional segregations were induced in In0.95Ga0.05Sb crystals by the addition of excess constituent elements, In, Ga, or Sb. The addition of excess Ga increased point defects, whereas excess Sb reduced dislocation densities. The thermoelectric figure of merit value (ZT) of In0.95Ga0.05Sb+Ga0.02 was recorded to be 0.87 at 573 K, which is the highest among other reported values of III-V semiconductors. The collective interactions of compositional segregations, point defects, and dislocations with electrons and phonons enhanced the ZT in this study.

Excellent thermoelectric properties and significant anisotropy for filled-tetragonal NaZnAs caused by strong anharmonicity

We have theoretically investigated the transport properties of the filled-tetrahedral NaZnAs using first-principles calculations in combination with self-consistent phonon theory and the Boltzmann transport equation. The results show that the transport behavior of NaZnAs exhibits obvious anisotropy, and the influence of quartic anharmonicity on the lattice thermal conductivity cannot be neglected as shown by the thermal conductivity results obtained from different computational models. Both the increase in scattering rates(SRs) and the decrease in group velocity signify a strong anharmonicity. We further find that the special vibrational modes due to the weak bonding of Zn atoms are the main source of anharmonicity. We find that considering the bubble diagram for the phonon self-energy correction reduces the κL by up to 28.04% at 700 K, which favors the capture of large ZT values. In addition, The ZT value of NaZnAs can reach 3.07 at 700 K, which shows great potential for thermoelectric applications.