Dimensionless Figure Of Merit Research Articles

Glassy ZIF-62 compositing induces ultralow lattice thermal conductivity in GeTe

A glassy zeolitic imidazolate framework-62 (g-ZIF-62) is used to composite with GeTe for effectively enhancing the mid-frequency phonon scattering to decrease the thermal conductivity of GeTe. After compositing, g-ZIF-62 distributes at the grain boundary of GeTe, leading to reduced lattice thermal conductivity (κl) of 0.31 W m–1 K–1 at 673 K, which is close to the theoretical amorphous limit of GeTe. Meanwhile, the introduction of g-ZIF-62 refrains the hall mobility and electrical conductivity, thus leading to minimized electrical thermal conductivity (κe). Accordingly, such g-ZIF-62 compositing can solely increase the ZT (dimensionless figure of merit) of GeTe of around 32 % at 723 K, even though the other parameters are not technically optimized for improving thermoelectric properties of GeTe. This study suggests that compositing g-ZIF-62 with GeTe can effectively strengthen the mid-frequency phonon scattering to decrease κl and κe of GeTe, providing a reasonable way to enhance the ZT of the thermoelectric materials.

Enhancement of thermoelectric performance by stacking fault control in (GeTe)1-x(Bi2Te3)x compounds, synthesized by hot press sintering method

We investigated the thermoelectric (TE) properties of GeTe by incorporating Bi2Te3 in the GeTe system. The addition of Bi2Te3 into the GeTe matrix leads to phonon scattering caused by stacking fault or structural defect, resulting in a substantial reduction in lattice thermal conductivity κlat. We observed a significant decrease in total thermal conductivities in the vertical and horizontal pressing directions, respectively. The optimized carrier properties and low thermal conductivity in the composites have led to a remarkable improvement in the dimensionless figure of merit (zT) 1.26 at 650 K. This study highlights the potential for creating high-performance thermoelectric materials through GeTe-Bi2Te3 compounds, emphasizing the importance of defect engineering and stacking faults in reducing thermal conductivity and improving thermoelectric efficiency.

Gradient Doping Enables an Extraordinary Efficiency in Thermoelectric PbTe1-xIx.

The conversion efficiency of thermoelectric generators that have to be operated under a temperature difference (ΔT) is mainly determined by material's dimensionless figure of merit (zT). However, maximization of zT at each temperature requires an optimization of carrier concentration (nopt) which strongly depends on the temperature and band parameters. Commonly utilized strategy of chemical doping usually enables a homogeneous carrier concentration throughout the material, leading the maximal zT to be achievable only within a narrow temperature range. In this work, a gradiently doping is successfully realized in PbTe1-xIx using a vertical gradient solidification technique, enabling a spatial gradient in carrier concentration that correspondingly optimizes zT at each portion of the material under its operating temperature. Such a gradient doping results in an extraordinary device efficiency of ≈14% at a ΔT of ≈500K, corresponding to a ≈40% improvement as compared to that of homogeneous doping. Since directional solidification technique commonly enables gradient dopant concentrations in semiconductors, the resultant gradient carrier concentration is illustrated here as an effective approach for advancing thermoelectrics.

Vacancy modulation dramatically enhance thermoelectric performance of InTe single crystal

InTe single crystals have demonstrated great promise in the field of thermoelectric materials, particularly when oriented along the [110] direction. This specific crystal orientation exhibits higher electronic conductivity and lower thermal conductivity compared to other orientations of InTe. Through first-principles calculations, we identified the anisotropic valence band and phonon dispersion as the underlying factors. Moreover, reducing the density of In+ vacancies in InTe was found to lower the band effective mass and modulate carrier scattering, enhancing the material quality factor (B). To explore these findings, we systematically grew InTe single crystals, achieving exceptional thermoelectric performance. A record-breaking power factor of 12.0 μW·cm–1·K–2 and a dimensionless figure of merit (zT) of 0.5 at room temperature were obtained. Notably, InTe crystals oriented along [110] with low In+ vacancy density exhibited the highest average zT of 0.63 among InTe-based thermoelectric materials within the 300–473K temperature range. Furthermore, we introduced an effective method of reducing In+ vacancies through Indium vapor annealing, resulting in the highest reported carrier mobility of 182 cm2·V–1·s–1 for InTe. Our study highlights the potential for improving InTe's thermoelectric performance near room temperature through vacancy modulation and crystal orientation.

Crystal growth and thermoelectric properties of Sn-doped Bi2Se3

We have studied the crystal growth of SnxBi2Se3 (x = 0 ∼ 0.75) and examined the effect of Sn doping on the structure and thermoelectric properties of Bi2Se3. All the crystal samples of SnxBi2Se3 were synthesized using a direct melt-growth. The results indicated that when the Sn doping content was ≤ 0.3, some Sn atoms were incorporated into the interlayers of Bi2Se3, thereby increasing the carrier concentration. In the intermediate to the high-temperature range, Sn doping improved the electrical conductivity of Bi2Se3, resulting in overall good performance in the power factor(PF). All the doped samples exhibited good ZT (a dimensionless figure of merit) in the intermediate to the high-temperature range, especially with the doping sample of x = 0.3 showing a maximum ZT value of 0.2 at 835 K.

Thermoelectric properties of Ga-doped InSb alloys

Internal structure and thermoelectric properties of In1-xGaxSb alloys, prepared by melting synthesis at 1123 K, were systematically studied in this paper. Crystal structure was investigated by XRD analysis. All samples exhibited crystalline structure of single InSb phase. Transport and electrical properties were studied against temperature elevating. Electrical conductivity was determined via the standard four probe method. The thermal behavior of the electrical conductivity over the temperature range between 273 K and 473 K showed semiconducting behavior. Seebeck coefficient measurements were conducted via differential method in the temperature range 273–473 K. The measurements of Seebeck coefficient confirmed the electrical conductivity behavior of the samples. The maximum obtained Seebeck coefficient value |S| of the parent InSb compound was observed at 224 μV/K, obtained at 273 K. The alloy has been doped with Ga in order to enhance thermoelectric properties. Results showed that introducing of Ga into In sites leads to significant increase in the Seebeck coefficient up to 330.4 μV/K. Power factor was estimated from the measurements of the electrical conductivity and the Seebeck coefficient. Interesting enhancement in the thermoelectric power factor was observed with Ga-doping. The maximum power factor was obtained for the most doped sample exhibiting 2.3 μWm−1 K−2 at 273 K. The thermal conductivity was obviously reduced by substituting In with Ga. The dimensionless figure of merit was estimated showing an enhancement with the Ga addition. The maximum recorded ZT was 0.017 observed at 403 K.

Synergetic effect of Bi and Al co-doping in GeTe-based thermoelectric materials leading to optimized carrier concentration tuning and high ZT

Improving the performance of thermoelectric (TE) materials that can convert waste heat into electricity is becoming increasingly important. Accordingly, the dimensionless figure of merit, ZT needs to be increased. Al, a group-III element, has not been widely used as a dopant in GeTe-based thermoelectric materials because it acts as a p-type dopant and thus further increases the hole carrier concentration of GeTe, which has already a high intrinsic hole concentration due to inherent Ge vacancies. Therefore, Al as a dopant in GeTe has been considered to have detrimental effects on the resulting thermoelectric performance. In this study, we aim to enhance the suitability of Al doping in GeTe-based materials through synergistically co-doping it with Bi. In this case, co-doping Al and Bi optimizes the carrier concentration and induces a high Seebeck coefficient from an additional increased effective mass and low total thermal conductivity arising from the numerous phonons scattering centers and decreased electronic contribution to heat transport. Consequently, a maximum ZT of ∼1.95 at 673 K with an increased average ZT is achieved. These results indicate that the p-type dopant Al, co-doped with Bi in GeTe-based thermoelectric materials is one of the very effective dopants which can eventually improve the overall TE performance of these materials for useful waste heat recovery application and cooling.

Enhanced thermoelectric performance via quantum confinement in a metal oxide semiconductor field effect transistor for thermal management

The performance of thermoelectric devices is gauged by the dimensionless figure of merit {{{{{boldsymbol{ZT}}}}}}. Improving {{{{{boldsymbol{ZT}}}}}} has proven to be a formidable challenge given the interdependence of its constitutive quantities, namely Seebeck coefficient, electrical conductivity, thermal conductivity, and temperature. Here, we use quantum confinement to decouple Seebeck coefficient and electrical conductivity to demonstrate an order of magnitude quantum-based enhancement to the thermoelectric figure of merit {{{{{boldsymbol{ZT}}}}}} in complimentary metal-oxide-semiconductor field-effect transistors. While most quantum-based enhancement is done through physical confinement using two-dimensional materials, our approach uses electrical confinement. Because of this, our device is more robust than the two-dimensional materials currently used. We further articulate that improvement by as much as a factor of 50 could be achieved in a practical setting. Our approach further provides a path for monolithic integration of on-chip coolers and energy scavengers with virtually no deviation from the fabrication flow of standard electronics.

Figure-of-Merits (FOM) for Direct Current TENG (Triboelectric Nanogenerator): Structural vs Dimensionless

This review paper provides a detailed overview of figure-of-merits (FOM) of Direct Current triboelectric nanogenerators (DC-TENGs). TENG represent a potentially ground-breaking technology for extracting mechanical energy from the environment. The FOM is a critical parameter that determines the efficiency of the energy conversion. This paper discusses the various working modes of DC-TENGs and also the research done to maximize output charge density. The review looks at recent different FOMs that could be formulated to improve the analysis of the performance and efficiency of TENGs more accurately. Finally, the paper concludes with a comparison between two different types of FOMs namely structural FOMs and dimensionless FOMs. It provides a valuable resource for researchers working in the field of TENGs and it sheds light on the key factors that influence the FOM of DC-TENGs. This enables the development of more efficient energy harvesting devices.

Rapid Free Electron Reduction in Plasma Irradiated Microscale Water Droplets

Many reaction studies show that microdroplets can provide a new avenue for green chemistry by enabling the electrochemical activity of water molecules. The observation of enhanced chemical reaction rates in gas-phase microdroplets compared to bulk liquids, often by orders of magnitude, has sparked considerable research interest. A number of factors may be involved, including evaporation enhanced reactant concentration, partial solvation at the surface, high surface to bulk number ratio, enhanced surface rate constants, pH gradients, gas-phase reactions and mass transfer, electric field enhancement and surface charging. Plasma interactions with liquids involve the mass transfer and accommodation of reactive radicals and other plasma chemical species, often occurs in the presence of high electric field and temperature gradients, UV flux and electric currents.We have investigated the use of low temperature atmospheric pressure plasma irradiated liquid microdroplets. [1] Picolitre microdroplets are totally surrounded by plasma and their high surface area relative to volume receives chemical, photon and charge flux during flight leading to chemical reactions in the liquid at low temperature. With the inclusion of precursors, the small volume provides an excellent basis for gas phase chemical microreactors that can deliver products continuously and almost instantaneously downstream for applications such as plasma medicine and specialist chemical or nanomaterial printing.In particular, low temperature plasmas are a copious source of free electrons, up to 106 times greater than corona discharges, which can interact with the liquid surface to promote rapid reduction reactions and possibly on-water catalysis. We have observed the reduction of metal salts in flight to produce nanoparticles at rates many orders of magnitude greater than standard solution chemistry or via radiolysis. [2] We have measured the plasma gas temperature in the presence of microdroplet streams with droplet rates up to 5 x 104 s-1 and observed no significant increase in gas temperature, which is typically ~300 K, thus keeping the evaporation limited. [3] Recently, we carried out plasma simulations, coupled with downstream chemical flux measurements, to determine the evolution of gas-phase chemistry in the plasma and effluent. [4] We have also performed the first measurements of plasma charging of particles, at atmospheric pressure for diameters > 1 um. The determined average droplet charge per droplet was 2.5 x 106 electrons (400 fC). Using a number of plasma particle charging models we estimate the electron flux ranged from 5 x 1022 m-2 s-1 to 4 x 1025 m-2 s-1.In [2], at least 50% Au3+ to Au0 reduction of the droplet precursor (HAuCl4) was observed over a ~120 µs plasma flight time and the equivalent Au0 generation rate is ~1013 atoms s-1. The ratio of electron flux per droplet to metal generation rate provides a dimensionless figure of merit, e-/Au0, of ~100 - 1000. Using plasma chemistry simulations along with estimates of electron flux to the droplet surface, we then simulated the subsequent water reactions using a 1-D radial reaction – diffusion scheme. For 15 µm diameter droplets without precursor, surface H2O2 concentrations ranged from 0.1 M to 100 µM whereas surface OH· concentrations were almost constant (~1 mM), as electron flux density (m-2 s-1) increased. However the OH· concentration decayed rapidly with depth, reaching 1 nM within 1 µm. As the droplet size increased, surface concentration and penetration depth both decreased. For electron flux densities up to ~5 x 1022 m-2 s-1, the solvated electron surface concentration was ~0.1 mM and the penetration depth was ~250 nm but at higher fluxes, the penetration depth increases significantly likely due to the reduced concentration of sub-surface H2O2 and OH·, which scavenge electrons. When 1 mM HAuCl4 precursor is added, the surface electron concentration and penetration depth is significantly reduced (< 50 nm), even at very high flux densities. We also observe the loss of surface Au3+ and the increase in Au0 concentration. However, the maximum overall conversion rate is 15%, compared to the experimental observation of >50%. Enhanced conversion would likely require greater precursor transport from droplet centre to surface, either by internal fields or convection. We carried out preliminary simulations of (Au0)N (N: 2 → 20) cluster growth via simple collisions in this environment and observed almost complete conversion of Au0 to cluster (Au0)N with the concentration of (Au0)20 >> (Au0)2.[1] PD Maguire et al., Appl. Phys. Lett. 106, 224101 (2015); doi: 10.1063/1.4922034[2] PD Maguire et al., Nano Lett., 17, 1336–1343 (2017) doi: 10.1021/acs.nanolett.6b03440[3] N Hendawy et al 2020 Plasma Sources Sci. Technol. 29 085010 doi: 10.1088/1361-6595/aba2aa[4] H McQuaid et al 2022, in-press. See preprint - doi: 10.48550/arXiv.2207.04518

Oxide Materials for Thermoelectric Conversion.

Thermoelectric technology has emerged as a prominent area of research in the past few decades for harnessing waste heat and improving the efficiency of next-generation renewable energy technologies. There has been rapid progress in the development of high-performance thermoelectric materials, as measured by the dimensionless figure of merit (ZT = S2 · σ · κ-1). Several heavy-metal-based thermoelectric materials with commercial-level performance (ZT = 1) have so far been proposed. However, the extensive application of these materials still faces challenges due to their low thermal/chemical stability, high toxicity, and limited abundance in the Earth's crust. In contrast, oxide-based thermoelectric materials, such as ZnO, SrTiO3, layered cobalt oxides, etc., have attracted growing interest as they can overcome the limitations of their heavy-metal-based counterparts. In this review, we summarize the recent research progress and introduce improvement strategies in oxide-based thermoelectric materials. This will provide an overview of their development history and design schemes, ultimately aiding in enhancing the overall performance of oxide-based thermoelectric materials.

Lattice plainification advances highly effective SnSe crystalline thermoelectrics

Thermoelectric technology has been widely used for key areas, including waste-heat recovery and solid-state cooling. We discovered tin selenide (SnSe) crystals with potential power generation and Peltier cooling performance. The extensive off-stoichiometric defects have a larger impact on the transport properties of SnSe, which motivated us to develop a lattice plainification strategy for defects engineering. We demonstrated that Cu can fill Sn vacancies to weaken defects scattering and boost carrier mobility, facilitating a power factor exceeding ~100 microwatts per centimeter per square kelvin and a dimensionless figure of merit (ZT) of ~1.5 at 300 kelvin, with an average ZT of ~2.2 at 300 to 773 kelvin. We further realized a single-leg efficiency of ~12.2% under a temperature difference (ΔT) of ~300 kelvin and a seven-pair Peltier cooling ΔTmax of ~61.2 kelvin at ambient temperature. Our observations are important for practical applications of SnSe crystals in power generation as well as electronic cooling.

High thermoelectric performance of mesostructured closely packed silicon powder

We report TE properties of mesostructured closely packed silicon powder facilely fabricated by die-pressing without sintering. Seebeck coefficient of Si-FeSi2 (13 wt% FeSi2) composite powder was between 100 ∼ 148 μV/K, with maximum power factor (PF) ∼ 0.164 mW/m⋅K2 at 400 K (pure Si powder ∼ 0.03 mW/m⋅K2). Boosted by the very low thermal conductivity (0.58 W·m−1·K−1), the dimensionless figure of merit, ZT value of Si-FeSi2 composite powder, ∼ 0.112, was obtained at 400 K, which is about 10 times higher than that of the bulk Si.

Phase, Crystal Structure, and Thermoelectric Performance of Cubic Skinnerite Cu3Sb1-yFeyS3 Synthesized by Mechanical Alloying

Skinnerite (Cu3SbS3) has recently attracted attention as a promising thermoelectric material because of its low thermal conductivity. In this study, we performed the solid-state synthesis of Fe-doped skinnerite Cu3Sb1-yFeyS3 (y = 0.02−0.06) using mechanical alloying and hot pressing, and examined the samples’ thermoelectric properties relative to Fe doping content. All samples contained only a cubic skinnerite phase, as evidenced by X-ray diffraction. As the Fe content increased, the lattice constant decreased from 1.03370 to 1.03310 nm, indicating successful substitution of Fe at the Sb sites. The carrier concentration increased with the Fe doping level, resulting in increased electrical conductivity. The specimens with y = 0.02− 0.04 exhibited non-degenerate semiconductor behavior, where the electrical conductivity increased as the temperature increased. In contrast, a specimen with y = 0.06 changed conduction behavior to the degenerate state with minimal temperature dependence. As the Fe content increased, the Seebeck coefficient decreased, and Cu3Sb0.98Fe0.02S3 exhibited a maximum power factor of 1.16 mWm-1K-2 at 623 K. Thermal conductivity values for all specimens were lower than 1.20 Wm-1K-1 in the measured temperature range but were higher than undoped skinnerite. The highest thermoelectric performance was achieved by the Cu3Sb0.98Fe0.02S3 specimen, with a dimensionless figure of merit, ZT, of 0.9 obtained at 623 K.

Thermoelectric properties of La-doped A-site SrTiO3 ceramics synthesised by the sol-gel auto-combustion technique

ABSTRACT Sr(1– x )La x TiO3 (SLTO) nanopowder (x = 0, 0.01, 0.05, 0.07, and 0.10) were effectively synthesised by the sol-gel auto-combustion process. Bulk ceramics samples were produced by spark plasma sintering (SPS) in an Ar atmosphere. The XRD pattern of the undoped SLTO nanopowder showed the pure phase and the impurity phase (TiO2) was detected in the La-doped SLTO samples. However, the impurity phase disappeared after producing the bulk samples with the SPS process. All the samples exhibited a negative Seebeck coefficient (S). The electrical conductivity (σ) and negative Sof all the SLTO samples increased with increasing temperature and reached a maximum value at 800 K. The thermal conductivity (κ) decreased with increasing temperature and increasing La content. The SLTO with x = 0.01 showed the largest σ, negative S, power factor (S 2 σ) and dimensionless figure of merit (ZT) at 800 K.

Multiple electron & phonon scattering effect achieves highly efficient thermoelectricity due to nanostructuring

To enhance the thermoelectric efficiency of a material, the decoupling of transport parameters in the dimensionless figure of merit, zT is important. The SnTe with MnTe magnetic nanoprecipitates was synthesized resulting in a high figure of merit. The gigantic localized spin moment of MnTe nanoprecipitates effectively scatters the conduction electron in SnTe, decoupling Seebeck coefficient, S, and electrical conductivity, σ. As a result, the powerfactor, S2σ was enhanced dramatically over the entire temperature range. The localized spin moment of MnTe nanoprecipitates was significantly larger than that of conventional magnetic atomic substitution in the alloy. Therefore, the spin moment fluctuation of superparamagnetic nanoprecipitates could effectively scatter electrons even at a high temperature. The first quantitative theoretical analysis for electron scattering was conducted in this work, to verify the spin dependent scattering. The weak localization measurement also supported the enhanced electron scattering by localized spin moment. The coherent MnTe nanoprecipitates in the SnTe matrix also reduced lattice thermal conductivity significantly. The slight difference in the lattice parameter between matrix SnTe and precipitates MnTe induced lattice strain and enhanced phonon scattering. The thermoelectric figure of merit zT was recorded 1.8 at 923 K in the eco-friendly material.

Evolution of defect structures leading to high ZT in GeTe-based thermoelectric materials

GeTe is a promising mid-temperature thermoelectric compound but inevitably contains excessive Ge vacancies hindering its performance maximization. This work reveals that significant enhancement in the dimensionless figure of merit (ZT) could be realized by defect structure engineering from point defects to line and plane defects of Ge vacancies. The evolved defects including dislocations and nanodomains enhance phonon scattering to reduce lattice thermal conductivity in GeTe. The accumulation of cationic vacancies toward the formation of dislocations and planar defects weakens the scattering against electronic carriers, securing the carrier mobility and power factor. This synergistic effect on electronic and thermal transport properties remarkably increases the quality factor. As a result, a maximum ZT > 2.3 at 648 K and a record-high average ZT (300-798 K) were obtained for Bi0.07Ge0.90Te in lead-free GeTe-based compounds. This work demonstrates an important strategy for maximizing the thermoelectric performance of GeTe-based materials by engineering the defect structures, which could also be applied to other thermoelectric materials.

High-temperature thermoelectric properties of (1-x)DyBCO − xBNT ceramics

ABSTRACT Dysprosium barium copper oxide – bismuth sodium titanate ((1-x)DyBCO−xBNT) ceramics, where x = 0−0.07 mole fraction, were successfully prepared by a solid-state reaction and sintering method. The DyBa2Cu3O7-δ and (Bi0.5Na0.5)TiO3 powders were separately synthesized by calcining their stoichiometric mixtures at 900°C for 4 h and 800°C for 2 h, respectively. The (1-x)DyBCO−xBNT powders were compacted into pellets and sintered at 930°C for 2 h under normal air atmosphere. Phase identification and morphology of all samples were determined using X-ray diffractometer (XRD). The quantitative phase analysis was analyzed by fitting the XRD pattern using the GSAS-II program. Scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS) was used to study microstructure and chemical composition. In all cases, the result of XRD shows that the DyBa2Cu3O7–δ (Dy-123) was identified as the main crystalline phases, due to the good agreement between the observed and calculated patterns after Rietveld refinement. All BNT-doped DyBCO ceramics showed slightly higher density values than the undoped sample, suggesting that BNT helped improve the densification process. The sign of the Seebeck coefficient () was positive for all samples at all measured temperatures, confirming a p-type conduction mechanism. Low BNT doping improved the overall thermoelectric properties of DyBCO ceramics by affecting electrical conductivity (), Seebeck coefficient (), and thermal conductivity (). The dimensionless figure of merit () of all samples increased with increasing temperature. The highest value of 5.67 × 10−2 was observed for the 0.97DyBCO−0.03BNT sample at 863 K.

Thermoelectric Properties of Co-Substituted Al-Pd-Re Icosahedral Quasicrystals.

The practical application of quasicrystals (QCs) as thermoelectric materials makes icosahedral (i-) Al–Pd–Re QC attractive because of its moderate electrical conductivity (~280 Ω−1 cm−1), relatively high Seebeck coefficient (~100 μV K−1), and low thermal conductivity (~1.3 W m−1 K−1) at room temperature. To develop a thermoelectric Π-shaped power generation module, we need both p- and n-type thermoelectric materials. In this work, we aimed to develop an n-type i-Al–Pd–Re-based QC and investigated the effect of Co substitution for Re on the thermoelectric properties, i.e., the electron-doping effect. We synthesized dense bulk samples with nominal compositions of Al71Pd20(Re1−xCox)9 (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) via arc-melting, annealing, and sintering methods. We found that Co can produce n-type carriers in dilute substitution amounts of x = 0.1 and 0.2; however, the Seebeck coefficient at 300 K showed an n- to p-type transition with increasing x. This indicates that a simple rigid-band approximation is not applicable for i-Al–Pd–Re QC, which makes it difficult to synthesize an n-type i-Al–Pd–Re-based QC. Although the thermal conductivity was reduced from 1.28 (x = 0) to 1.08 W m−1 K−1 (x = 0.3) at 373 K by lowering of the electron thermal conductivity (electrical conductivity) and the alloying effect via Co substitution, the dimensionless figure of merit was not enhanced because of lowering of the power factor for all samples. The elastic moduli of i-Al–Pd–Re QC decreased by Co substitution, indicating that i-Al–Pd–Re-Co QC had a more ionic and brittle character.

Incompletely Decomposed In4SnSe4 Leads to High‐Ranged Thermoelectric Performance in n‐Type PbTe

AbstractAdditives in thermoelectric materials are conventionally considered as either extrinsic defects or second phases regardless of their dynamic processes. Herein, In4SnSe4, with inherent low thermal conductivity, is introduced into n‐type PbTe. It is revealed that In4SnSe4 decomposes incompletely at high temperatures, in which around 80% of In4SnSe4 dissolves into InSe and Sn, while 20% forms as nano‐precipitates. Benefiting from the incomplete decomposition, PbTe‐0.1%In4SnSe4 presents superior thermoelectric performance compared to the stepwise and compositionally identical PbTe‐0.4%InSe‐0.1%Sn. The residual In4SnSe4 along with Sn and InSe jointly contribute to the synergetic optimization of carrier mobility and lattice thermal conductivity in PbTe‐0.1%In4SnSe4. As a result, the room‐temperature dimensionless figure of merit (ZT) of ≈0.4 and the ZTave of ≈0.83 at 300–573 K are obtained, and an experimental maximum thermoelectric conversion efficiency (η) of ≈2.5% (ΔT ≈ 400 K) is obtained, demonstrating significant research progress in n‐type PbTe. This work indicates that the In4SnSe4 incomplete decomposition effectively decouples the electron and phonon transports in n‐type PbTe and the strategy of utilizing the unstable additives is proven feasible. Additionally, more dynamic behaviors of additives are worth expecting and may promote more achievements for other thermoelectric systems.