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CrN-based alloy thin films are of interest as thermoelectric materials for energy harvesting. Ab initio calculations show that dilute alloying of CrN with 3 at. % W substituting Cr induce flat electronic bands and push the Fermi level EF into the conduction band while retaining dispersive Cr 3d bands. These features are conducive for both high electrical conductivity σ and high Seebeck coefficient α and, hence, a high thermoelectric power factor α2σ. To investigate this possibility, epitaxial CrWxNz films were grown on c-sapphire by dc-magnetron sputtering. However, even films with the lowest W content (x = 0.03) in our study contained metallic h-Cr2N, which is not conducive for a high α. Nevertheless, the films exhibit a sizeable power factor of α2σ ∼ 4.7 × 10−4 W m−1 K−2 due to high σ ∼ 700 S cm−1, and a moderate α ∼ − 25 μV/K. Increasing h-Cr2N fractions in the 0.03 < x ≤ 0.19 range monotonically increases σ, but severely diminishes α leading to two orders of magnitude decrease in α2σ. This trend continues with x > 0.19 due to W precipitation. These findings indicate that dilute W additions below its solubility limit in CrN are important for realizing a high thermoelectric power factor in CrWxNz films. [ABSTRACT FROM AUTHOR]

Graph neural networks (GNNs) have evolved many variants for predicting the properties of crystal materials. While most networks within this family focus on improving model structures, the significance of atomistic features has not received adequate attention. In this study, we constructed an atomistic line GNN model using compositionally restricted atomistic representations which are more elaborate set of descriptors compared to previous GNN models, and employing unit graph representations that account for all symmetries. The developed model, named as CraLiGNN, outperforms previous representative GNN models in predicting the Seebeck coefficient, electrical conductivity, and electronic thermal conductivity that are recorded in a widely used thermoelectric properties database, confirming the importance of atomistic representations. The CraLiGNN model allows optional inclusion of additional features. The supplement of bandgap significantly enhances the model performance, for example, more than 35% reduction of mean absolute error in the case of 600 K and 10 19 cm − 3 concentration. We applied CraLiGNN to predict the unrecorded thermoelectric transport properties of 14 half-Heusler and 52 perovskite compounds, and compared the results with first-principles calculations, showing that the model has extrapolation ability to identify the thermoelectric potential of materials. [ABSTRACT FROM AUTHOR]

We attempted to deposit a platinum (Pt) layer onto a tungsten trioxide (WO3) thin film (Pt/WO3). The Pt layer deposited on WO3 was oxidized by calcining Pt/WO3 in air to form PtOx/WO3. An n-type anomalous photo-thermoelectric (photo-TE) effect was confirmed for Pt/WO3 and Pt/HyWO3−x. HyWO3−x is a protonated WO3 after the gaschromic (GC) reaction of WO3 in Pt/WO3. The anomalous photo-TE effect was that both the electrical conductivity (σphoto) and the absolute value of the Seebeck coefficient (Sphoto) increased under UV light or visible light irradiation. After stopping the irradiation, σphoto and Sphoto decreased. In contrast, an n-type normal photo-TE effect was observed for PtOx/HyWO3−x after the GC reaction of PtOx/WO3, in which σphoto increased and the absolute value of Sphoto decreased under ultraviolet (UV) light irradiation, and vice versa after stopping the irradiation. These findings indicate that Pt was responsible for the anomalous photo-TE effect due to the electron accumulation capability of Pt, to which electrons were transferred from the conduction band of HyWO3−x. In contrast, electrons could not energetically transfer from HyWO3−x to PtO2, which existed in PtOx particles at the surface. Therefore, PtOx/HyWO3−x behaved similar to sole HyWO3−x, indicating the normal photo-TE effect. [ABSTRACT FROM AUTHOR]

Magnons are quasiparticles of spin waves, carrying both thermal energy and spin information. Controlling magnon transport processes is critical for developing innovative magnonic devices used in data processing and thermal management applications in microelectronics. The spin ladder compound S r 14 C u 24 O 41 with large magnon thermal conductivity offers a valuable platform for investigating magnon transport. However, there are limited studies on enhancing its magnon thermal conductivity. Herein, we report the modification of magnon thermal transport through partial substitution of strontium with yttrium (Y) in both polycrystalline and single crystalline S r 14 − x Y x C u 24 O 41. At room temperature, the lightly Y-doped polycrystalline sample exhibits 430% enhancement in thermal conductivity compared to the undoped sample. This large enhancement can be attributed to reduced magnon-hole scattering, as confirmed by the Seebeck coefficient measurement. Further increasing the doping level results in negligible change and eventually suppression of magnon thermal transport due to increased magnon-defect and magnon-hole scattering. By minimizing defect and boundary scattering, the single crystal sample with x = 2 demonstrates a further enhanced room-temperature magnon thermal conductivity of 19 W m − 1 K − 1 , which is more than ten times larger than that of the undoped polycrystalline material. This study reveals the interplay between magnon-hole scattering and magnon-defect scattering in modifying magnon thermal transport, providing valuable insights into the control of magnon transport properties in magnetic materials. [ABSTRACT FROM AUTHOR]

2D Janus Rashba semiconductors, which break both the mirror symmetry in the crystal structure and the spin degeneracy in the energy band, provide a promising platform to optimize thermoelectric performance. Herein, we use first-principles and Boltzmann transport theory to investigate the electron and phonon transport properties for Janus semiconductors of monolayer Si2AsSb and Si2SbBi. The strong Rashba spin-splitting is found in both Janus monolayers especially for Si2SbBi, which decreases the bandgaps and makes the valence bands more dispersive, resulting in decreased p-type Seebeck coefficient and increased p-type electrical conductivity. The lattice thermal conductivities of both monolayers are not low due to the weak phonon anharmonicity, strong chemical bonding, and long phonon relaxation time. The low lattice thermal conductivity of Si2SbBi than Si2AsSb mainly originates from the low phonon group velocity. Both monolayers exhibit better thermoelectric performance in n-type than in p-type. The competition among Seebeck coefficient, electrical conductivity, and electronic thermal conductivity makes the difference of optimal thermoelectric figure of merits in n-type without and with Rashba spin–orbit coupling slight for Si2AsSb, but it is significant for Si2SbBi. Within Rashba spin–orbit coupling, the optimal figure of merits at 700 K reach 0.65 and 0.59 for Si2AsSb and Si2SbBi, respectively, which indicate the potential thermoelectric applications, and will stimulate the broad study on thermoelectric properties of 2D Janus Rashba semiconductors. [ABSTRACT FROM AUTHOR]

Magnons are quasiparticles of spin waves, carrying both thermal energy and spin information. Controlling magnon transport processes is critical for developing innovative magnonic devices used in data processing and thermal management applications in microelectronics. The spin ladder compound S r 14 C u 24 O 41 with large magnon thermal conductivity offers a valuable platform for investigating magnon transport. However, there are limited studies on enhancing its magnon thermal conductivity. Herein, we report the modification of magnon thermal transport through partial substitution of strontium with yttrium (Y) in both polycrystalline and single crystalline S r 14 − x Y x C u 24 O 41. At room temperature, the lightly Y-doped polycrystalline sample exhibits 430% enhancement in thermal conductivity compared to the undoped sample. This large enhancement can be attributed to reduced magnon-hole scattering, as confirmed by the Seebeck coefficient measurement. Further increasing the doping level results in negligible change and eventually suppression of magnon thermal transport due to increased magnon-defect and magnon-hole scattering. By minimizing defect and boundary scattering, the single crystal sample with x = 2 demonstrates a further enhanced room-temperature magnon thermal conductivity of 19 W m − 1 K − 1 , which is more than ten times larger than that of the undoped polycrystalline material. This study reveals the interplay between magnon-hole scattering and magnon-defect scattering in modifying magnon thermal transport, providing valuable insights into the control of magnon transport properties in magnetic materials. [ABSTRACT FROM AUTHOR]

This work presents the excess noise and thermoelectric (Seebeck) measurements on polycrystalline vanadium dioxide (VO2) thin films. Noise spectral power density (SPD) of current fluctuations in the semiconducting (SC) phase had a typical flicker noise (f−γ) characteristic with an average slope parameter γ of 1.13. Normalized SPD (Sn) values obtained in the SC-phase indicate that the noise originates in the bulk of the film. On the contrary, in the metallic (M)-phase, γ values were greater than unity, and the observed Sn values indicated that the origin of the noise is most likely from the contacts or surface rather than the bulk. A general decrease was observed in Sn by a factor of 4–5 from the SC- to M-phase. Moreover, Sn in the SC-phase showed no temperature dependence. An interpretation based on the number of charge carrier fluctuations in Hooge's model led to an unrealistically high Hooge parameter and had to be ruled out. We propose that the fluctuations are related to the mobility fluctuations of carriers arising primarily from grain-boundary scattering which explains the observed characteristics well. The Seebeck coefficients (S) obtained under both heating and cooling schedules showed the n-type nature of magnetron-sputtered VO2 films in the SC-phase. Differently, in the M-phase, the S value was positive. The S values obtained from the cooling schedule signified the low percolation threshold of the metal-to-insulator transition already demonstrated for VO2 thin films grown on r-cut sapphire using the Efros–Shklovskii percolation model. [ABSTRACT FROM AUTHOR]

This study aimed to determine various thermoelectric properties, including the dimensionless figure of merit (zT0), resistivity (ρTE), thermal conductivity (κTE), and Seebeck coefficient (S), using a combination of 3ω and time-domain impedance spectroscopy (TDIS) methods for a thermoelectric module at absolute temperature (T0). The effective dimensionless figure of merit (zT0,eff), influenced by heat leakage through attached lead wires, was quantitatively and qualitatively assessed based on the TDIS method. The results demonstrated that zT0,eff/zT0 can be expressed as the ratio between the thermal conductance of the attached thermoelectric element and the lead wire. Thus, by considering heat leakage through the lead wire, the TDIS method can estimate not only zT0 and ρTE but also κTE and S after measuring the lead wire's thermal conductivity using the 3ω method. The study utilized a commercial Π-shaped bismuth-telluride-based thermoelectric module and derived representative values for its elements. zT0, ρTE, κTE, and |S| at 300 K were 0.871, 10.15 μΩ m, 1.71 W/mK, and 224 μV/K, respectively, consistent with previous reports on representative bismuth-telluride-based materials. In conclusion, the combination of the 3ω and TDIS methods is useful for determining all thermoelectric properties, considering heat leakage through attached lead wires. [ABSTRACT FROM AUTHOR]

Different from the extensive experimental investigations into the thermoelectric (TE) properties of the bulk IV–VI compounds, less attention has been paid to the TE properties of the monolayer IV–VI compounds. Here, we consider the TE transport properties including the Seebeck coefficient, electronic conductance, thermal conductance, power factor, and figure of merit Z T of the undoped and Bi-doped GeS monolayers. Our results show that for both the undoped and Bi-doped monolayers the anisotropy is widely observed in all their TE properties, and the maximum Z T at a certain temperature along the armchair direction is much greater than that along the zigzag direction. Moreover, Bi doping can lead to an increase of the maximum Z T , and there are more Z T peaks appearing near the zero chemical potential. This indicates that the Bi-doped GeS monolayer can work as a TE material at a lower bias voltage, and especially along the armchair direction it can work at zero bias voltage, which obviously strengthens the reliability of the TE devices. As the temperature increases, the maximum Z T will be uniformally increased along the armchair and zigzag directions for both the undoped and Bi-doped GeS monolayers. In the temperature scope from 300 to 800 K, the maximum Z T along the armchair direction of the Bi-doped GeS monolayer will increase from 3.39 to 4.85, which indicates that this Bi-doped GeS monolayer is a promising TE material in a wide-temperature zone. As an application, we have designed the GeS-based TE couples and found that their efficiencies can be greater than 27 % at large temperature differences. This research should be an important guidance for designing a low-voltage, wide-temperature-scope, and high-stability TE device. [ABSTRACT FROM AUTHOR]

MXenes exhibit significant potential in thermoelectric materials owing to their exceptional electrical conductivity; however, their limited number of semiconductors restricts their application. Thus, it is highly desirable to expand the MXene family beyond carbides and nitrides to broaden their applications in thermoelectricity. In this work, we systematically investigate the thermoelectric transport of Ti2OX2 (X = F, Cl) MOene through comprehensively evaluating the electron–phonon coupling (EPC) from first principles. Our findings first emphasize the limitations of the deformation potential theory method and stress the importance of considering EPC. Ti2OF2 (Ti2OCl2) monolayer exhibits exceptional electronic transport, with Seebeck coefficients reaching 1483.87 (1206.22) μV/K and electrical conductivity reaching 9.5 × 105 (7.6 × 105) Ω−1 m−1 at room temperature for its N-type counterpart. Additionally, the presence of degenerate multiple valleys and peaks significantly enhances their electronic transport. For phonon transport, EPC results in a significant reduction in lattice thermal conductivity (kL) [e.g., at 300 K with 1.44 × 1015 (1.68 × 1015) cm−2 of hole, the reduction is 86.3% (73.3%) for Ti2OF2 (Ti2OCl2)]. Additionally, their kL demonstrates a strong correlation with the density of states at corresponding Fermi levels. Moreover, the kL and total thermal conductivity of P-type Ti2OF2 show T-independence, making it suitable for applications in aviation and thermal insulation materials. Finally, N-type Ti2OF2 and Ti2OCl2 demonstrate superior zT values of 0.63 and 0.9 at 900 K, respectively. This study provides in-depth insights into the superior thermoelectric properties of Ti2OX2 (X = F, Cl) MOene with considering EPC, providing a novel platform for the next-generation thermoelectric field. [ABSTRACT FROM AUTHOR]

Despite more than seven decades of active research and development in thermoelectricity, the accurate measurement of the thermoelectric (TE) properties of bulk materials has remained a challenge, mainly because of the strong interrelation between thermal and electrical phenomena. This work highlights practical advancements in methods and instrumentation dedicated to the simultaneous measurements of TE properties such as the Seebeck coefficient (S), the thermal (κ), and electrical (σ) conductivities and the dimensionless TE figure of merit ZT = S2σT/κ. The accuracy of a Harman based approach, as implemented by the ZT-Scanner (TEMTE Inc.), applicable to the simultaneous measurement of the above TE properties, has been made possible by a self-contained calibration procedure, which is based on the availability of two samples of the same homogeneous material having different shape factors. It is of practical importance that this approach provides a simple procedure to obtain the calibration for the figure of merit ZT and the thermal conductivity in the temperature interval from 300 to 720 K. In addition, we show that a simplified Harman setup with no thermocouples attached to the sample can also be used for self-contained calibrated ZT measurements. It is concluded that the implemented steady-state approach decreases the relative error down to 1%–2% for ZT measurements and can be recommended for most applications not involving dynamical behavior. In particular, it is proposed that self-generated calibration samples can critically increase the quality and ease of comparison of TE measurements if they are adopted by the TE community. [ABSTRACT FROM AUTHOR]

In this study, we systematically investigated the anomalous Nernst effect in perpendicularly magnetized amorphous TbFeCo thin films with various compositions. It was found that the magnitude of the off diagonal thermopower (ODT), which corresponds to the anomalous Nernst effect, can be uniformly explained with respect to the Tb content regardless of the concentration above or below the compensation composition. The maximum ODT of 1.3 μ V/K and the thermoelectric conductivity of 1.59 A/mK at room temperature were obtained, which is more significant than other perpendicular magnetic anisotropy thin films to achieve a large Nernst voltage for roll-type thermoelectric devices. By considering the thermoelectric tensor, Mott's equation, and the scaling law, it was shown both experimentally and theoretically that the magnitudes of the first and second terms contributing to the anomalous Nernst effect are comparable. It was also found that the ODT of TbFeCo thin films is twice or more significant than the product of the Seebeck coefficient and the Hall angle. Furthermore, amorphous metals and Mn-alloys with a large Berry curvature are located above the relation that the ODT is twice the product of the Seebeck coefficient and the Hall angle, which means that amorphous metals are expected to enhance the ANE. [ABSTRACT FROM AUTHOR]

In this study, the basic properties of Ba2AgSi3 were investigated in detail from both experimental and computational viewpoints. Polycrystalline Ba2AgSi3 formed by an arc-melting apparatus under an argon atmosphere was ground into powders, and then powder samples were sintered using the spark plasma sintering method. Both n-type and p-type samples were obtained. This may be due to a slight deviation from the stoichiometric composition. The energy bandgap of Ba2AgSi3 was measured to be around 0.17 eV from the temperature dependence of electrical conductivity and was in agreement with that by first-principles calculations. Sintered samples exhibited a high Seebeck coefficient of −273 μV K−1 and a high power factor of 0.38 mW m−1 K−2 at 307 K for n-type samples. They were 217 μV K−1 and 0.23 mW m−1 K−2, respectively, at 320 K for p-type samples. The electronic structures of impurity-doped Ba2AgSi3 were also discussed using first-principles calculations to investigate the insertion site of impurity atoms. The calculations suggest that the substitution of B (P) at any Si site shifts the Fermi level and transforms it into p-type (n-type) semiconductors. On the other hand, substitution of Ba or Ag sites with B or P is unlikely to occur in terms of formation energy. [ABSTRACT FROM AUTHOR]

We present an atomistic simulation of thermoelectric properties in cove-edged graphene nanoribbons (CGNRs) via the nonequilibrium Green's function. Different from gapless zigzag graphene nanoribbons (ZGNRs), CGNRs exhibit a noticeable bandgap. Such a bandgap can be modulated by varying three structural parameters (namely, the width N, the distance between adjacent coves m, as well as the shortest offset n) of CGNRs, which can give rise to the transition from semiconducting to semi-metallic. Due to the less dispersive phonon bands and the decrease in the number of phonon channels of CGNRs, they are found to have the lower phonon thermal conductance than ZGNRs. Modulation of CGNRs can produce over tenfold improvement of the maximum of ZT compared to ZGNRs. This improvement is due to the promotion of the Seebeck coefficient together with the degradation of the phonon thermal conductance of CGNRs compared to ZGNRs. [ABSTRACT FROM AUTHOR]

To achieve high-performance optoelectronic devices and thermoelectric behaviour, non-stoichiometric compositions have been utilised in ternary transition metal dichalcogenides. This study marks the first report on the growth of CuxSb1−xSe2 (x = 0.2, 0.4, 0.6, 0.8) crystals using the Bridgman technique. We investigated the impact on their structural, optical, thermal and electrical properties in comparison with pure CuSbSe2. Powder X-ray diffraction confirmed the presence of the dominant orthorhombic CuSbSe2 phase along with minor secondary phases and this result was well supported by Raman spectroscopy. The crystallite size increases from 12 nm to 27 nm while the lattice strain decreases from 0.0116 to 0.0054 with Cu content in the crystal. Elemental analysis carried out by EDAX has reflected the desired stoichiometry of each crystal. FESEM images have shown flat as well as layer growth on their surfaces, thereby giving an indication that the growth of crystals occurred by a layer-by-layer growth mechanism. Raman spectra indicated the red shift in the Ag vibrational mode of CuSbSe2 with increasing Cu proportion. The direct bandgap of each crystal is reduced from 1.55 eV to 1.42 eV with higher Cu percentage which is determined from the Kubelka–Munk function using the recorded reflectance spectrum which shows that these crystals can be promising candidates for optoelectronic applications. The positive value of the Seebeck coefficient (S) demonstrates the p-type semiconducting nature of each crystal measured in the temperature range of 323 K to 593 K. Among the grown crystals, P3 (Cu0.6Sb0.4Se2) exhibited the superior power factor and ZT values of 0.0182 μW cm−1 K−2 and 0.935 × 10−4 at 595 K, respectively. The TGA of each crystal demonstrated single step decomposition, showcasing a maximum weight loss of 18.07% for the P4 crystal, which is confirmed by DTG. To assess the photodetection properties of each crystal, I–V curves and pulse photoresponses are recorded in parallel to plane configuration. Among all grown crystals, the P3 (Cu0.6Sb0.4Se2) crystal based photodetector exhibits superior responsivity and detectivity of 0.014 mA W−1 and 5.656 × 108 Jones, respectively. These findings show that these crystals can be considered as a choice for thermoelectric as well as photodetection applications. [ABSTRACT FROM AUTHOR]

The development of Ga-doped Zinc Oxide (GZO) films from nontoxic, abundant elements using a cost-effective and scalable approach is crucial for the profitability and sustainability of thermoelectric applications. Challenges in formulating GZO film inks have led to extensive experimentation to enhance their thermal, structural, mechanical, and room-temperature thermoelectric properties by adjusting ink concentration and annealing treatment. Increasing the GZO nanoparticle concentration reduced the melting temperature and crystallinity, whereas annealing at 200 °C decomposed the polyethylene oxide (PEO) binder. TEM analysis revealed the polycrystalline structure of the GZO nanoparticles and their interaction with the binder, while XRD patterns confirmed the characteristic peaks of the GZO films; annealing effectively eliminated the PEO diffraction peaks. The GZO films from the concentrated 1.24M ink exhibited minimal grain growth, reduced lattice strains, uniform elemental distribution, and enhanced surface texture and conductivity, which were further improved by annealing. Increasing the GZO nanoparticle concentration facilitated the formation of a conductive network, while annealing enhanced the conductivity by promoting the formation of a cohesive, interconnected network through impurity removal, nanoparticle redistribution, and coalescence. Consequently, the annealed 1.24M film demonstrated the highest nanohardness of 791 MPa and a thermoelectric power factor of 1.78 nW/m∙K2 at room temperature, which were attributed to enhanced electrical conductivity and Seebeck coefficient through concentration and annealing synergies. [ABSTRACT FROM AUTHOR]

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 (Sn 1-x Bi x Te 0.97 Se 0.03 (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 Sn 0.94 Bi 0.06 Te 0.97 Se 0.03 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 Sn 0.96 Bi 0.04 Te 0.97 Se 0.03 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. [Display omitted] [ABSTRACT FROM AUTHOR]

The thermoelectric properties of polycrystalline copper (Cu) surfaces partially covered with graphene grown by Joule‐heating chemical vapor deposition using scanning thermoelectric microscopy are investigated. Atomic‐resolution atomic force microscopy topographic images of graphene grown on Cu(100) surfaces showed a 1D stripe pattern of Moiré superlattices, while thermoelectric voltage images clearly distinguish wrinkle defects caused by thermal mismatch between graphene and Cu substrate. Regions of different signs were found in the thermoelectric voltage image of the graphene island, which are attributed to the faceted surface of the Cu substrate. In addition, faceted surfaces consisting of low‐ and high‐index Cu surfaces are formed on the Cu grain to minimize the surface energy. Due to these structural changes, charge transfer and chemical interactions at the interface between the graphene and Cu facets affect the electronic structure of the graphene, which is understood as the observed Seebeck coefficients with different signs in the thermoelectric microscopy measurements, which are sensitive to the local density of states. [ABSTRACT FROM AUTHOR]

In this paper, a series of S 0. 0 5 Co4Sb 1 1. 6 Te 0. 4 samples were prepared by high pressure and high temperature (HPHT) method under different pressures. The synthesis time was shortened from several days to 0.5 h. Te doping and S filling simultaneously optimized the thermal and electrical transport properties of the CoSb3 materials. We found a porous architecture containing rich grain boundaries, different grain sizes, nano- to micrometer-sized pores, and a large number of dislocations, which can scatter a wide spectrum of phonons. Seebeck coefficient α , electrical resistivity ρ , and thermal conductivity κ were measured between 295 K and 773 K. The minimum thermal conductivity of S 0. 0 5 Co4Sb 1 1. 6 Te 0. 4 synthesized at 3.0 GPa was 1.23 Wm − 1  K − 1 , and its maximum zT value reached 1.07 at 773 K, especially the lattice thermal conductivity was as low as 0.49 Wm − 1  K − 1 . [ABSTRACT FROM AUTHOR]

The behavior of the Seebeck coefficient in the intermediate regime between atomic scale ballistic conduction and bulk-like diffusive conduction remains unclear. To address this, we have developed a microscale device capable of simultaneously measuring the Seebeck coefficient and electrical conductance of gold nanowires in an adiabatic environment. The nanowires were made in situ by electromigration from lithographically prepared bow-tie electrodes, yielding a wide range of wire thicknesses down to a few hundred atoms. We observed quantization of the Seebeck coefficient, a phenomenon previously observed only at the Ångstrom scale, in relatively thick wires with a thickness of several tens of nanometers. The quantized Seebeck coefficient was proportional to the reciprocal of the electrical conductance with a slope of − 47.8 μ V / K , indicating that electrons are spatially confined due to the electronic shell structure of the nanowire, similar to the quantization of electrical conductance. [ABSTRACT FROM AUTHOR]

This study utilizes density functional theory (DFT) and the Boltzmann transport equation (BTE) to investigate the structural, electronic, and thermoelectric properties of germanium sulfide (GeS) and germanium selenide (GeSe) monolayers, along with their van der Waals (vdW) heterostructures. We analyzed XX-stacked and XY-stacked configurations, where the XX configuration features direct atomic stacking, while the XY configuration exhibits staggered stacking. Our first-principles calculations indicate that the formation of GeS/GeSe heterostructures results in a reduction of bandgaps compared to their bulk and monolayer counterparts, yielding bandgap values of 0.91 eV for the XX configuration and 0.84 eV for the XY configuration. Stability assessments reveal that the XY configuration is more stable, demonstrating a lattice thermal conductivity of 15.21 W/mK compared to 17.95 W/mK for the XX configuration T 300 K. The thermoelectric properties were systematically evaluated across a temperature range of 300–800 K, revealing high Seebeck coefficients of 1.51 mV/K for the XX heterostructure and 1.39 mV/K for the XY heterostructure. reflecting their excellent charge transport capabilities. Notably, the figure of merit (ZT) at 800 K was calculated to be 0.90 for the XX configuration and 1.01 for the XY configuration, underscoring the superior thermoelectric performance of the XY heterostructure. These findings contribute to a comprehensive understanding of 2D GeS/GeSe heterostructures for thermoelectric applications and provide a solid foundation for future research and technological advancements in this domain. [ABSTRACT FROM AUTHOR]

Spintronics, micro/nanofabrication, and the semiconductor industry are undergoing significant transformations, highlighting the need for flexible technologie. This study examines the possibility of integrating topological insulators (TIs), specifically Bi2Te3 thin films (13–191 nm), into flexible spintronic applications through scalable magneto‐sputtering techniques, and investigates how structural organization influences electrical and topological properties through post‐thermal annealing. Films annealed above 250 °C display improved polycrystalline structure, larger crystallites, fewer local defects, and higher a room‐temperature Seebeck coefficient (S) and resistivity (ρ), suggesting decreased bulk electronic contributions. A metastable transport regime is identified in the temperature‐dependent resistivity of films annealed at 300 °C between 20–100 K; in this range, the thinnest film exhibits markedly metallic behavior, signaling the presence of topological surface states (TSS). Magnetoresistance measurements of as‐grown and annealed films, between 3–20 K, demonstrate weak antilocalization. Applying the Hikami‐Larkin‐Nagaoka model, α‐coefficients are found to scale with thickness from 0.5–1, indicating thickness‐controlled coupling of the TSS. Post‐annealing at 300 °C, the phase coherence length, Lϕ, of the thinner films increases, while the temperature dephasing rate shifts from ∼0.7 (as‐grown) to ∼0.5 (post‐annealing), aligning with expected values for 2D TSS. These are encouraging findings for large‐scale manufacturing flexible TI technologies, without sacrificing tunabilit. [ABSTRACT FROM AUTHOR]

The thermoelectric material PdSe2$\left(\text{PdSe}\right)_{2}$ in orthorhombic (Pbca) phase is studied with the help of density functional theory implemented in WIEN2k. The main properties of PdSe2$\left(\text{PdSe}\right)_{2}$ investigated are elastic, electronic, and thermoelectric properties. The anisotropy factors obtained with the elastic constants indicate that PdSe2$\left(\text{PdSe}\right)_{2}$ is strongly anisotropic. The Tran and Blaha‐modified Becke–Johnson exchange potential is used for bandgap calculations. The BoltzTraP code is used to find out the thermoelectric properties of PdSe2$\left(\text{PdSe}\right)_{2}$. At 300 K, the maximum value of the Seebeck coefficient is 200 μV K−1 for the hole carrier concentration of 2.5 × 1019 cm−3 and is 241 μV K−1 for the electron carrier concentration of 1.2 × 1019 cm−3. The power factor (PF) and figure of merit (ZT) are calculated for different carrier concentrations and temperatures. The optimum value of ZT for bulk PdSe2 as calculated in this work is ≈0.6 for hole carrier concentration (p = 2.6 × 1020 cm−3) at 800 K, which suggests PdSe2$\left(\text{PdSe}\right)_{2}$ as a potential material in thermoelectric applications at higher temperatures. [ABSTRACT FROM AUTHOR]

We herein introduce a microwave-assisted solid state technique to synthesize zintl compounds YbCd 2-x Zn x Sb 2 (0.0 ≤ x ≤ 2.0) in short time of 10 min by utilizing an active carbon as a susceptor material. Here, we report an energy-saving preparation route using a domestic microwave oven. A microwave susceptor material rapidly heats the elemental starting materials inside an evacuated quartz ampoule resulting in near single phase compounds. By studying the crystal structure using X-Ray diffraction (XRD) and SEM-EDS, the hexagonal crystal structures of the prepared samples were identified. Thermoelectric characterizations have been performed for all obtained samples and among them the compound YbCd 1. 6 Zn 0.4 Sb 2 is found as the best one because it has Seebeck coefficient of −22.68 μV/k, and power factor of 8.20 μWcm−1k−2 at 523 K with carrier concentration of 3.04 × 1021 cm−3 at 300 K. [ABSTRACT FROM AUTHOR]

The Bi 2 Sr 2 Co 2 O y ceramic, known for its stability as a p-type thermoelectric material, has limited thermoelectric performance that necessitates enhancement. In this study, Bi 2- x Cu x Sr 2 Co 2 O y (x = 0, 0.025, 0.05, 0.1, 0.2) ceramic samples were synthesized using the conventional solid-state reaction method. Substitution of Cu2+ for Bi3+ in the samples increased carrier concentration, significantly reducing electrical resistivity. Utilizing the single parabolic band (SPB) model, it was determined that Cu incorporation led to an increased effective mass, thereby enhancing the Seebeck coefficient. Additionally, fine grains and lattice defects induced by Cu2+ substitution effectively scattered phonons, resulting in an ultra-low thermal conductivity of 0.59 Wm−1K−1 at 923 K for the Bi 1.8 Cu 0.2 Sr 2 Co 2 O y sample. Consequently, Cu substitution optimized both the electrical and thermal transport properties of Bi 2-x Cu x Sr 2 Co 2 O y samples. The dimensionless thermoelectric figure of merit (ZT) for Bi 1.95 Cu 0.05 Sr 2 Co 2 O y reached 0.31 at 923 K, representing a 63 % increase over the pristine Bi 2 Sr 2 Co 2 O y sample. [ABSTRACT FROM AUTHOR]

The current work discusses on the effect of sodium (Na) and bismuth (Bi) ion doping at different concentrations in the compositional formula La0.67Sr0.33–yNay/2Biy/2MnO3 (y = 0, 0.0825, 0.165, 0.2475, 0.33) on structural, magnetic, magnetotransport and thermoelectric studies. X-ray diffraction confirms the R c space group with rhombohedral structure and the field emission scanning electron microscope images confirms a systematic growth of grains with increasing in NaBi concentrations. An enhancement in the ferromagnetic ordering and magnetic transitions above 325 K were observed up to y = 0.165 and they decrease thereafter. A broad maximum along with a double peak behavior were noticed in the temperature dependent resistivity curves and they disappear upon the application of external magnetic fields. The Seebeck coefficient show a change of sign from positive to negative with increasing temperature for lower concentrations of NaBi and they exhibit a negative sign for higher substitutions suggesting the variation in the nature of charge carriers. The small polaron hopping mechanism governs the resistivity and thermopower behavior in the high temperature regions while, electron-electron, electron-magnon, magnon-magnon scattering mechanism contributes in the low temperature region. [ABSTRACT FROM AUTHOR]

We present the theoretical and experimental results for the full Heusler alloys Mn2MAl for late 3d transition metals – M = Fe, Co, Ni. For the first time, the synthesized Mn2CoAl and Mn2NiAl alloys crystallize in the β-Mn- and B2-types crystal structure. The electronic structure and magnetic properties of the alloys were investigated within the framework of first-principles theoretical calculations. It was revealed that the alloys have metallic properties and antiparallel alignment of the large Mn magnetic moments and almost compensated total magnetic moments. In addition, we investigated the effect of electronic correlations on the electronic structure and magnetic properties of the alloys within DFT + U method that resulted in a negligible effect for the total magnetic moments of Mn2MAl (M = Fe, Co, Ni). The frequency dependence of the real and imaginary parts of the dielectric constant is measured in the spectrum region of 0.1–5 eV. In order to characterize thermoelectric properties of the studied Heusler alloys, we performed measurements of electrical resistivity and calculated Seebeck coefficient. The results are interpreted based on our theoretical calculations and different structural compositions. [ABSTRACT FROM AUTHOR]

The effect of temperature on the electrical conductivity (σ) and Seebeck coefficient (S) of n-type vapor grown carbon nanofibers (CNFs) and poly(vinylidene fluoride) (PVDF) melt-mixed with 15 wt% of those CNFs is analyzed. At 40 °C, the CNFs show stable n-type character (S=−4.8 µV·K−1) with an σ of ca.165 S·m−1, while the PVDF/CNF composite film shows an σ of ca. 9 S·m−1 and near-zero S (S=−0.5 µV·K−1). This experimental reduction in S is studied by the density functional tight binding (DFTB) method revealing a contact electron transfer from the CNFs to the PVDF in the interface. Moreover, in the temperature range from 40 °C to 100 °C, the σ(T) of the CNFs and PVDF/CNF film, successfully described by the 3D variable range hopping (VRH) model, is explained as consequence of a thermally activated backscattering mechanism. On the contrary, the S(T) from 40 °C to 100 °C of the PVDF/CNF film, which satisfactorily matches the model proposed for some multi-walled carbon nanotube (MWCNT) doped mats; however, it does not follow the increase in S(T) found for CNFs. All these findings are presented with the aim of discerning the role of these n-type vapor grown carbon nanofibers on the σ and S of their melt-mixed polymer composites. [ABSTRACT FROM AUTHOR]

Mg3Sb2-based materials, part of the Zintl compound family, are known for their low thermal conductivity but face challenges in thermoelectric applications due to their low energy conversion efficiency. This study addressed these limitations through first-principles calculations using the CASTEP module in Materials Studio 8.0, aiming to enhance the thermoelectric performance of Mg3Sb2 via strategic doping. Density functional theory (DFT) calculations were performed to analyze electronic properties, including band structure and density of states (D.O.S.), providing insights into the influence of various dopants. The semiclassical Boltzmann transport theory, implemented in BoltzTrap (version 1.2.5), was used to evaluate key thermoelectric properties such as the Seebeck coefficient, electrical conductivity, electronic thermal conductivity, and electronic figure of merit (eZT). The results indicate that doping significantly improved the thermoelectric properties of Mg3Sb2, facilitating a transition from p-type to n-type behavior. Bi doping reduced the band gap from 0.401 eV to 0.144 eV, increasing carrier concentration and mobility, resulting in an electrical conductivity of 1.66 × 106 S/m and an eZT of 0.757. Ge doping increased the Seebeck coefficient to −392.1 μV/K at 300 K and reduced the band gap to 0.09 eV, achieving an electronic ZT of 0.859 with low thermal conductivity (11 W/mK). Si doping enhanced stability and achieved an electrical conductivity of 1.627 × 106 S/m with an electronic thermal conductivity of 11.3 W/mK, improving thermoelectric performance. These findings established the potential of doped Mg3Sb2 as a highly efficient thermoelectric material, paving the way for future research and applications in sustainable energy solutions. [ABSTRACT FROM AUTHOR]

Heat pumping through thermoelectric devices has many advantages over traditional cooling. However, their current efficiency is a limiting factor in their implementation. In this paper, we approach the non-convex topology optimization of thermoelectrical elements for cooling applications through the method of moving asymptotes (MMA) to improve their cooling capabilities per watt usage. The optimization problem is defined for a given power budget, aiming for the minimum temperature with a known heat pumping need. The introduction of power as a constraint justifies the introduction of the voltage gradient across the thermocouple as a design variable to maintain the thermoelectrical device in its optimum power-to-heat extraction ratio. To better understand the convergence of this non-convex problem, we present a two-variable analytical thermoelectric optimization model. This example provides information on how to select the penalty parameters used to scale the three material coefficients involved in the problem to obtain lower objective values and better convergence using MMA. The analytical model shows the non-convexity of the problem and provides the recommendation to use penalization coefficients of the form p k = p σ > p α = 1 for the thermal conductivity, electrical conductivity, and Seebeck coefficients. We tested these penalization coefficients through optimizations of a model based on the 1MC10-031 commercial thermoelectric-cooler (TEC) using the finite element method (FEM). These penalization coefficients provided local minima without the need for volume constraints. With this procedure, we found designs that provided temperatures close to 10 degrees lower using 60% less semiconductor material volume compared to the initial design. [ABSTRACT FROM AUTHOR]

This study investigates the structural, optoelectronic, magnetic and thermophysical properties of three newly designed semiconductor pyrochlore oxides, namely RE2Ti2O7 (RE = Er, Eu, Tb), using ab-initio calculations within the density functional theory framework. The values of indirect bandgaps are 3.8, 2.2 and 3.77 eV for the spin up channel of Er2Ti2O7, Eu2Ti2O7, and Tb2Ti2O7, respectively. While the values of indirect bandgaps for the spin down channel of Er2Ti2O7, Eu2Ti2O7, and Tb2Ti2O7 are 3.56, 3.65 and 2.1 eV, respectively. The paramagnetic magnetic moments can be inferred by analyzing the distinct band shapes observed in the energy band structures of the studied compounds corresponding to the spin up and spin down states. The magnetic moments of Er2Ti2O7, Eu2Ti2O7, and Tb2Ti2O7 have significant magnitudes, specifically measuring 12.00, 24.51, and 24.00 μ B , respectively. Significant absorption of incident photons by the studied compounds can be noted in near UV region in both spin channels. Low reflectivity (~ 30%) by RE2Ti2O7 (RE = Er, Eu, Tb) is evident from the R (ω) spectra in an energy range of 1.0–10.0 eV. However, these compounds exhibit ~ 50% reflectance of the incident photons in upper UV region (above 10.0 eV). The analysis of the Seebeck coefficient spectra reveals that RE2Ti2O7 (RE = Er, Eu, Tb) exhibits p-type semiconductor behavior, however, Eu2Ti2O7 also shows n-type behavior from 200 to 450 K. The presented thermodynamic characteristics reveal that the pyrochlore oxides RE2Ti2O7 (RE = Er, Eu, Tb) exhibit thermal stability. [ABSTRACT FROM AUTHOR]

Ab-initio simulations using density functional theory (DFT) were employed to investigate the structural, mechanical, electronic, magnetic, optical, and thermoelectric properties of halide perovskites (X = Cl, Br, I). Structural optimization and mechanical stability assessments confirm the reliability of these perovskites in a hexagonal P mc symmetry. The stability of the ferromagnetic phase was validated through total crystal energy minimization via Murnaghan's equation of state. Electronic band structures and density of states, derived from the generalized gradient approximation (GGA), reveal a semiconducting ferromagnetic nature in the spin up channel, spotlighting their potential in semiconductor spintronic applications. Phonon dispersion analysis of and revealed positive phonon modes throughout the entire Brillouin zone, confirming their dynamical stability. In contrast, demonstrated dynamical instability. The elastic constants confirm the mechanical stability and ductile nature of the perovskites. Optical and dielectric properties of these perovskites show significant UV absorption and photoconductivity, making them highly suitable for optoelectronic and solar cell applications. Finally, transport properties, such as the Seebeck coefficient, electrical conductivity, thermal conductivity, power factor, and figure of merit (ZT) unveil their exceptional thermoelectric performance. Combining half-metallic ferromagnetic traits with superior thermoelectric and optoelectronic performance positions compounds as exceptional candidates for applications in spintronics, optoelectronics, and thermoelectrics. This comprehensive investigation demonstrates their ability to excel across a diverse array of advanced technological applications. [ABSTRACT FROM AUTHOR]

Since SrTiO 3 is attractive due to its versatile electronic properties ranging from dielectric to semiconducting behavior, the effect of systematic co-substitution of various A-site cations on the electronic structure and transport properties of oxygen-deficient SrTiO 3- δ bulk ceramics was analyzed. The materials were synthesized by reverse co-precipitation method and densified by spark plasma sintering (SPS) in a vacuum, followed by a post-thermal treatment in a reducing atmosphere (5 % H 2 /Ar). The phase purity was confirmed by X-ray diffraction (XRD), different microstructures were revealed by scanning electron microscopy (SEM), and characterization in terms of electrical conductivity (σ el) and Seebeck coefficient (S) were performed. The largest power factor was obtained with Sr 0.25 Ca 0.25 Na 0.25 La 0.25 TiO 3-δ by maintaining electrical conductivity while increasing the Seebeck coefficient. Density Functional Theory (DFT) calculations were applied to obtain information on band structures, the projected density of states (PDOS), and electron density differences (EDD). Band structures indicated that oxygen deficiency essentially changed the conductive nature of the studied materials by shifting the Fermi level to the conductive zone, while PDOS plots define the role of each element located at the A site. The electronic structure is affected to the greatest extent in the cases when Nd and Pr are present at the A-site. However, the obtained experimental and computational (DFT) results could not completely match and explain all phenomena since understanding the effect of different cations at A-site on oxygen vacancy formation seems to be a challenging task, and therefore, some hypotheses are proposed. This work attempts to understand the role of a particular cation at A-site on the electronic band structure and its relevance to the formation of oxygen vacancies, thereby providing valuable insights for future high-entropy perovskite titanates with improved transport properties. [ABSTRACT FROM AUTHOR]

Thermally chargeable supercapacitors can collect low‐grade heat generated by the human body and convert it into electricity as a power supply unit for wearable electronics. However, the low Seebeck coefficient and heat‐to‐electricity conversion efficiency hinder further application. In this paper, we designed a high‐performance thermally chargeable supercapacitor device composed of ZnMn2O4@Ti3C2Tx MXene composites (ZMO@Ti3C2Tx MXene) electrode and UIO‐66 metal–organic framework doped multichannel polyvinylidene fluoridehexafluoro‐propylene ionogel electrolyte, which realized the thermoelectric conversion and electrical energy storage at the same time. This thermally chargeable supercapacitor device exhibited a high Seebeck coefficient of 55.4 mV K−1, thermal voltage of 243 mV, and outstanding heat‐to‐electricity conversion efficiency of up to 6.48% at the temperature difference of 4.4 K. In addition, this device showed excellent charge–discharge cycling stability at high‐temperature differences (3 K) and low‐temperature differences (1 K), respectively. Connecting two thermally chargeable supercapacitor units in series, the generated output voltage of 500 mV further confirmed the stability of devices. When a single device was worn on the arm, a thermal voltage of 208.3 mV was obtained indicating the possibility of application in wearable electronics. [ABSTRACT FROM AUTHOR]

The structure–property relationship at interfaces is difficult to probe for thermoelectric materials with a complex interfacial microstructure. Designing thermoelectric materials with a simple, structurally‐uniform interface provides a facile way to understand how these interfaces influence the transport properties. Here, we synthesized Bi2−xSbxTe3 (x = 0, 0.1, 0.2, 0.4) nanoflakes using a hydrothermal method, and prepared Bi2−xSbxTe3 thin films with predominantly (0001) interfaces by stacking the nanoflakes through spin coating. The influence of the annealing temperature and Sb content on the (0001) interface structure was systematically investigated at atomic scale using aberration‐corrected scanning transmission electron microscopy. Annealing and Sb doping facilitate atom diffusion and migration between adjacent nanoflakes along the (0001) interface. As such it enhances interfacial connectivity and improves the electrical transport properties. Interfac reactions create new interfaces that increase the scattering and the Seebeck coefficient. Due to the simultaneous optimization of electrical conductivity and Seebeck coefficient, the maximum power factor of the Bi1.8Sb0.2Te3 nanoflake films reaches 1.72 mW m−1 K−2, which is 43% higher than that of a pure Bi2Te3 thin film. [ABSTRACT FROM AUTHOR]

The emergence of new functionalities in transition metal oxides and their interfaces poses an important challenge. Many recent discoveries regarding the polar/nonpolar interface between perovskite oxides open new avenues for modern applications. SrTiO3/LaCrO3 heterostructures are particularly intriguing due to a polar discontinuity along the [001] direction, giving rise to two distinct and controllable interface structures, TiO2-LaO and SrO-CrO2, which exhibit new and promising electronic and thermoelectric transport properties. Through a combination of first-principles simulations based on density functional theory and the Boltzmann transport equation, we have calculate and discuss the structural, electronic, valence band offset, and thermoelectric properties of SrTiO3, LaCrO3, and SrTiO3/LaCrO3 heterostructures. The temperature dependence of the Seebeck coefficient, electrical conductivity, electronic thermal conductivity, and figure of merit is determined. Furthermore, we highlight the effect of the interface between the polar perovskite LaCrO3 and the nonpolar SrTiO3(001) on the thermoelectric properties, wherein we observed a change in the metal–semiconductor transport behavior. These results constitute an important advancement in our understanding of the thermoelectric properties at polar/nonpolar perovskite oxide interfaces. [ABSTRACT FROM AUTHOR]

Copper selenide (Cu2Se) has attracted extensive research interest in the field of thermoelectricity due to its large abundance of constituent elements, environmental friendliness, and excellent thermoelectric properties. In this study, a facile and low-cost hydrothermal synthesis method combined with vacuum sintering was used for Cu2Se-based sample preparation, and the possibility of improving the thermoelectric properties of Cu2Se by doping with rare earth elements (Tm, Er, Lu) was explored using experimental tests and density functional theory calculations. The electronic structure calculations show that the electrical conductivity is increased due to the increased electron density after rare earth element doping. At the same time, the sharp increase in the density of states at the Fermi level after rare earth element doping enhances the Seebeck coefficient of the Cu2Se matrix. The experimental results show that the thermoelectric properties of all the samples doped with rare earth elements (Tm, Er, Lu) were improved compared to the Cu2Se matrix. The doping of rare earth elements led to an increase in point defects and the formation of pores in the samples, which play an important role in reducing the thermal conductivity. Among them, the Tm-doped Cu1.995Tm0.005Se sample reached a maximum ZT value of 0.80 at 773 K, which is a nearly 43% increase compared to the Cu2Se matrix (ZTmax = 0.56). [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) GeTe is a popular medium-temperature thermoelectric material, but few studies have focused on strategies for improving its thermoelectric performance. To further investigate the thermoelectric properties of two-dimensional GeTe, different atomic defects are introduced, and the electronic structure and thermoelectric properties are systematically investigated via first-principles calculations and the semiclassical Boltzmann theory. Compared with that of three-dimensional (3D) GeTe, the Seebeck coefficient of 2D GeTe increases from 144 μV K−1 to 560 μV K−1 at 700 K, and the thermal conductivity decreases from 3.3 W m−1 K−1 to 2.3 W m−1 K−1. Thus, the ZT value increases from 0.8 to 1.14. On the basis of these results, the influence of vacancy atomic defects on the thermoelectric performance is investigated. With single-atom defects (SV-Ge and SV-Te), the ZT value increases at constant temperature. However, for double-atom defects in monolayer GeTe, the ZT value increases when DV-585 defects are present but decreases to varying degrees when DV-Ge and DV-Te defects are present. The ZT value of monolayer GeTe with DV-585 defects has an average increase of 0.56 at 300–800 K, which accords well with the experimental results. This study indicates that introducing single-atom vacancy defects somewhat improves the thermoelectric performance of monolayer GeTe, which provides an important point of reference for the development of GeTe in the two-dimensional materials field. [ABSTRACT FROM AUTHOR]

This study introduces the synthesis of a hybrid thermoelectric material with enhanced conductivity and a high Seebeck coefficient, leveraging the properties of Te nanowires (NWs) and the conductive polymer PEDOT:PSS. Te NWs were synthesized using the galvanic displacement reaction. To further enhance conductivity, Ag-Te NWs were synthesized under optimized conditions via the Ag topotactic reaction, achieving desired results within 7 min using ethylene glycol and AgNO3. This hybrid material exhibited an electrical conductivity of 463 S/cm, a Seebeck coefficient of 69.5 μV/K at 300 K, and a power factor of 260 μW/mK2. These metrics surpassed those of conventional Te/PEDOT:PSS hybrids by a factor of 3.6, highlighting the superior performance of our approach. This study represents a significant advancement in thermoelectric materials, improving both conductivity and efficiency. [ABSTRACT FROM AUTHOR]

Thermoelectric cooling materials based on Bi2Te3 have a long history of unsurpassed performance near room temperature. Recently, research into price‐competitive Mg3(Bi, Sb)2‐based materials are focused on replacing traditional cooling materials. Here, the thermoelectric properties of Mg3.2Bi1.998−xSbxTe0.002Cu0.005 (x = 0.0, 0.1, 0.2, 0.3, 0.4, and 0.5) polycrystalline compounds are investigated. In all temperature regions, electrical resistivity and Seebeck coefficient are increased with Sb concentration. The electronic transport properties of Sb‐alloyed compounds are maximized by synergistically combined band engineering approaches such as band structure change caused by lattice strain, increased electronic density of states, and chemical potential shift, leading to exceptionally high‐power factor values of over 3.0 mW m−1 K−2 at room temperature. Furthermore, with increasing Sb content, thermal conductivity values are systematically reduced due to the promotion of alloy scattering of phonons and suppression of the bipolar contribution. Consequently, these multiple approaches significantly enhance thermoelectric performance, resulting in an enhancement of thermoelectric figure‐of‐merit zT above 1.1 at 348–423 K. Additionally, a zTavg of 1.1 is recorded at 300–450 K, making it an unrivaled value among the reported n‐type Mg3Bi2‐based thermoelectric materials. Overall, this work demonstrates that Mg3Bi2‐based materials are more promising for thermoelectric cooling applications compared to Bi2Te3‐based materials. [ABSTRACT FROM AUTHOR]

Efficient and air‐stable molecular dopants are critical for optimizing the performance of thermoelectric devices. Despite significant advancements in developing p‐dopants for organic semiconductors, the quest for efficient and air‐stable n‐dopants remains challenging. Here, viologen‐tetraarylborate (VT) is introduced as a promising n‐dopant for thermoelectric applications, demonstrating its remarkable photo‐activation efficiency. After just 1 min of light exposure, a maximum power factor of 8.6 µW m−1 K−2, with a conductivity of 0.86 S cm−1 and a Seebeck coefficient of −346 µV K−1, is achieved for the VT doped PNDI2TEG‐2Tz film. Furthermore, VT exhibits excellent air stability, simplifying the device preparation process by allowing films to be prepared in ambient conditions. Additionally, the unique doping mechanism imparts good air stability to the stock solution of VT and the conjugated polymer, ensuring that the storage time of the stock solution does not affect thermoelectric performance. This innovative approach not only highlights the potential of VT as an efficient n‐dopant but also paves the way for developing novel air‐stable dopants and advancing doping methodologies in thermoelectric material research. [ABSTRACT FROM AUTHOR]

Tin sulfide (SnS) is widely recognized as a promising material for thermoelectrics owing to its layered structure, anharmonicity, earth abundance, and minimal toxicity. This study focuses on controlling the hole concentration of SnS by substituting isovalent Zn through a vacuum melting technique. The presence of point defects, such as mass fluctuations and strain field fluctuations, along with lattice dislocations and stacking faults, results in a drop in thermal conductivity. The mass difference between Zn dopant and Sn host atoms plays a significant role in point defect scattering when Zn is substituted in the SnS lattice. Additionally, variations in size and interatomic coupling forces between Zn and Sn atoms contribute to the amplification of point defect scattering, effectively reducing the lattice thermal conductivity. Furthermore, the diminished lattice thermal conductivity of SnS samples with Zn substitution is ascribed to the decreased phonon mean free path. The synergy of multi-scale scattering results in a low thermal conductivity of 0.88 W m−1 K−1 at 773 K. Further, Zn substitution slightly improved the carrier concentration from 6.88 × 1015 cm−3 to 2.31 × 1016 cm−3 resulting in enhanced electrical conductivity without the drastic decrement in the Seebeck coefficient. This in turn significantly improved the power factor to 42.6 μW m−1 K−2 for the Sn0.95Zn0.05S sample. [ABSTRACT FROM AUTHOR]

Thermoelectric (TE) materials are significant for sustainable development because they can be used to harvest waste heat into electricity. Organic TE materials have unique merits including high mechanical flexibility, low cost, and low intrinsic thermal conductivity. But their TE properties particularly the Seebeck coefficient are notably lower than the inorganic counterparts. Here, a poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) film is reported with a very high Seebeck coefficient and figure of merit (zT) at room temperature through secondary doping, dedoping engineering, and ionic energy filtering. The PEDOT:PSS films are successively treated with acid, base, and vitamin C that is a reductant, and then coated with 1‐ethyl‐3‐methylimidazolium dicyanamide (EMIM:DCA) that is an ionic liquid. This can exhibit a record‐high Seebeck coefficient and power factor of 111 µV K−1 and 1285 µW m−1 K−2, respectively, and the corresponding zT value is 1.05. This is the highest zT value for polymers and polymer composites, and it is comparable to that of the best inorganic TE materials. [ABSTRACT FROM AUTHOR]

Higher Manganese Silicides (HMS) are the best p-type materials beneficial for intermediate-temperature range thermoelectric device applications due to their high thermal stability and inexpensive constituent elements. Although the cost-effective HMS materials possess high thermal stability, they are concerned with high thermal conductivity values. The nanocomposite approach was promised to lower the thermal transport properties without affecting the electrical transport properties, which is experimented in the present work. The higher manganese silicide with varying weight percentages of nano-structured Si 0.8 Ge 0.2 B 0.02 inclusions was experimented to decrease the thermal conductivity and to enhance the electrical properties. The lowest thermal conductivity value of ≃ 2.24 W/mK was reported with 2 wt% Si 0.8 Ge 0.2 B 0.02 addition in HMS material. Also, the HMS-2 wt. % Si 0.8 Ge 0.2 B 0.02 improved the transport properties, electrical conductivity and Seebeck coefficient values of ≃ 4 × 104 S/m and ≃ 220 μV/K respectively. Furthermore, various mathematical models were proposed here to simulate the composite approach results, which were then correlated with experimental results. [ABSTRACT FROM AUTHOR]

Misfit‐layered calcium cobaltite [Ca2CoO3‐δ]0.62[CoO2] is an outstanding p‐type semiconducting thermoelectric with strong anisotropic properties. Texture engineering is crucial for enhancing its thermoelectric performance in polycrystalline ceramics. The in‐plane orientation of the grains improves the Seebeck coefficient and electrical conductivity, while the multi‐scale parallel interfaces scatter phonons and reduce thermal conductivity. Here, a tandem process of spark plasma sintering and edge‐free spark plasma texturing is used to produce dense and highly textured calcium cobaltite ceramics. The resulting ceramic shows a high degree of texturization, secondary phases, and enhanced electrical conductivity of 246 S cm−1 together with a strongly improved Seebeck coefficient of 224 µV K−1 at 1073 K. High grain ordering leads to carrier mobility of 0.49 cm2 V−1 s−1, which has a positive effect on both parameters. With a power factor of 12.4 µW cm−1 K−2 at 1073 K in air, previous thermoelectric performances of calcium cobaltite are surpassed, regardless of its form: pristine, doped, or composite. By combining the high power factor with a relatively low thermal conductivity, a remarkable figure‐of‐merit of 0.49 at 1073 K in air is obtained for the textured polycrystalline ceramic, which reaches 60 % of the figure‐of‐merit of a calcium cobaltite single crystal. [ABSTRACT FROM AUTHOR]

High‐performance polycrystalline calcium cobaltite ceramic was synthesized via electrospinning of nanoribbons, followed by dual‐process compaction using spark plasma sintering and edge‐free spark plasma texturing. The combination of nanoribbon electrospinning and this multistage sintering technique was employed for the first time and resulted in exceptionally well‐textured thermoelectric ceramics. The textured ceramic had excellent thermoelectric properties. At 1073 K, the ceramic exhibited an electrical conductivity of 268 S cm−1, a Seebeck coefficient of 247 µV K−1 and a heat conductivity of 3.3 W m−1 K−1. In addition, the power factor and figure‐of‐merit reached enormously high values of 16.3 µW cm−1 K−2 and 0.53, respectively. This represents the highest thermoelectric performance reported to date not only for electrospun, polycrystalline calcium cobaltite fiber ceramics, but also for undoped polycrystalline calcium cobaltite ceramics. [ABSTRACT FROM AUTHOR]

The large Nernst effect is advantageous for developing transverse Nernst thermoelectric generators or Ettingshausen coolers within a single component, avoiding the complexity of electron- and hole-modules in longitudinal Seebeck thermoelectric devices. We report a large Nernst signal reaching 130 μV/K at 8 K and 13 T in the layered metallic antiferromagnet EuAl2Si2. Notably, this large transverse Nernst thermopower is two orders of magnitude greater than its longitudinal counterpart. The Nernst coefficient peaks around 4 and 8 K at 3 and 13 T, respectively. At similar temperatures, both the Hall coefficient and the Seebeck signal change sign. Additionally, nearly compensated electron- and hole-like carriers with high mobility (∼ 4000 cm2/V s at 4 K) are revealed from the magnetoconductivity. These findings suggest that the large Nernst effect and vanishing Seebeck thermopower in EuAl2Si2 are due to the compensated electron- and hole-like bands, along with the high mobility of the Weyl band near the Fermi level. Our results underscore the importance of band compensation and topological fermiology in achieving large Nernst thermopower and exploring potential Nernst thermoelectric applications at low temperatures. [ABSTRACT FROM AUTHOR]

Higher manganese (TE) silicide (HMS), an eco-friendly, low-cost, and earth-abundant p-type thermoelectric material, exposes a Nowotny chimney-ladder crystal structure, obeying the 14th-electron rule. Here, a hybrid composite of a carbon nanofiber (CNF) and HMS was synthesized by vacuum melting followed by spark plasma sintering, and its thermoelectric performance were demonstrated. The incorporation of CNF with HMS notably enhances the Seebeck coefficient and decline the thermal conductivity without significantly affecting the carrier concentration and electrical conductivity due to the interfacial energy filtering effect. A maximum Seebeck coefficient of 307 μV/K was recorded for the 0.5% CNF composite with HMS, leading to accomplish a high-power factor of 1755.63 μW/mK2 at 803 K. Also, interfaces, grain boundaries, and dislocations leading to the high magnitude of strain, confirmed from HR-TEM and strain analysis, leads to decrease in lattice thermal conductivity to 1.95 W/mK. As a result, HMS attains the peak zT value of 0.64, suggesting that carbon-based composites are a promising way to boost the thermoelectric performance of HMS-based compounds. [ABSTRACT FROM AUTHOR]

Quasi‐solid‐state thermocells (QTECs) show promise as a power source for wearable devices by converting body heat into electricity. While significant progress has been made with p‐type elements for QTECs, challenges remain with their n‐type counterparts. Here, a high‐performance n‐type QTEC element is presented, using a copolymer hydrogel that outperforms conventional p‐type elements. This copolymer hydrogel combines hydrophilic zwitterionic sulfobetaine methacrylate (SBMA) for ionic conduction and hydrophobic methyl methacrylate (MMA) for structural stability. By increasing the MMA content from 35 to 100 wt.%, versatile control is achieved over the hydrogel's elastic modulus (72 kPa to 127.7 MPa) and tensile strength (54 kPa to 6.7 MPa). A high mechanical toughness of 7.2 MJ m−3 is also achieved at 68 wt.% MMA. The mechanically robust and high toughness p(SBMA‐MMA) hydrogel is then immersed in Fe(ClO4)2/3 solutions of different concentrations to evaluate its performance as an n‐type QTEC element. The hydrogel with 0.8 M Fe(ClO4)2/3 exhibits a high ionic Seebeck coefficient of −1.7 mV K−1, a power density of 1.1 mW m−2 K−2, and an elastic modulus of 1.6 MPa, which is similar to that of human skin. Finally, the optimized n‐type p(SBMA‐MMA) hydrogels demonstrate the potential application for wearable devices. [ABSTRACT FROM AUTHOR]

Since crystal structure dictates the resultant physical properties of materials, titled physical features of the P21 monoclinic SiGe semiconductors, which are still unclear, have been revealed by density functional theory (DFT). The electronic band gap value with 0.49 eV was found to be in the order of previously published cubic and hexagonal closed-packed SiGe semiconductors. Surprisingly, P21 monoclinic SiGe has a room temperature Seebeck coefficient of 1500 μ V/K which is higher than the reported data of both cubic and hexagonal SiGe alloys. Further, the mechanically stable P21 monoclinic phase of the SiGe displays a brittle mechanical character with clear elastic anisotropy has also been deduced. The P21 monoclinic phase of the SiGe can be also considered a good high-dielectric material and beneficial for practical applications of IR or UV goals due to its high refractive index. [ABSTRACT FROM AUTHOR]