Increase In Seebeck Coefficient Research Articles

Boosting the thermoelectric properties of n-type PbSe through the dual incorporation of Sb and Al

PbSe has attracted significant attention as a medium-temperature thermoelectric (TE) material due to its abundance and low cost. This study demonstrate that in the novel thermoelectric system of AlxPb0.9975Sb0.0025Se samples (x = 0, 0.005, 0.01, 0.02, and 0.03), the electronic conductivity of pure PbSe was enhanced by Sb doping. Introducing a small amount of Al to occupy the Pb vacancies not only increases the Hall carrier concentration in PbSe, but also resulting in an increase in Seebeck coefficient (S). At 873 K, the power factor (PF) of the sample with x = 0.02 increases to 16 μW cm−1 K−2. In addition, the total thermal conductivity did not increase significantly, so the thermoelectric performance was effectively improved, a maximum figure of merit (ZT) of 1.8 is achieved at 873 K, along with a high average ZT (ZTavg) of approximately 1 over the temperature range of 300–873 K.

Synergistic effects of hybrid n-doping on the thermoelectric performance and air-stability of water-processable single-walled carbon nanotubes

Organic thermoelectrics (TEs) based on carbon nanotubes (CNTs) have attracted much attention with their inherent advantages, such as, earth-abundant elements, broad electronic tunability, and excellent mechanical compliance. However, the inferior TE performance and doping stability of n-type CNTs to those of p-type CNTs have been bottlenecks to establish CNT-based next-generation TEs. Herein, we report a hybrid n-doping method that improves the n-type TE performance and long-term air-stability of water-processable single-walled CNT (SWCNT) and carboxymethyl cellulose (CMC) composite. The hybrid n-doping process with polyethyleneimine (PEI) n-dopant contains primary addition and secondary immersion doping, which causes a simultaneous increase in electrical conductivity and Seebeck coefficient through efficient n-doping and surface energy filtering effect, respectively. Furthermore, the hybrid-doped films exhibit superior long-term stability by inhibiting the oxidation of SWCNT/CMC at nanoscale, which allows to ensure the initial power factor even after storing in ambient for a month. Finally, we successfully demonstrated hybrid-doped SWCNT/CMC-based TEGs with long-term stable output characteristics. This work can offer insights to develop efficient and air-stable n-type organic TE materials and devices.

Enhancing the thermoelectric properties of PEDOT:PSS films through the incorporation of g-C3N4 nanosheets and carbon nanotubes

Present study focuses on the synthesis of flexible nanocomposite film made of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS), graphitic carbon nitride (g-C3N4) nanosheets, and carbon nanotubes (CNTs) and how the g-C3N4 nanosheets and CNTs affect the thermoelectric properties of PEDOT:PSS. Incorporating 10 wt% of g-C3N4 nanosheets to PEDOT:PSS improved the Seebeck coefficient to 74.3 μVK−1, ∼5 times higher than the PEDOT:PSS film. However, this led to a decrease in electrical conductivity, limiting the power factor to 335.4 μWm−1K−2. In order to address this, CNTs were added as conductive fillers. The resulting PEDOT:PSS composite, with 10 wt% of g-C3N4 and 10 wt% CNTs, showed a significant power factor of 589.8 μWm−1K−2, an electrical conductivity of 810.6 Scm−1, and a Seebeck coefficient of 84.5 μVK−1, indicating a substantial improvement in the thermoelectric performance of pristine PEDOT:PSS. The increased Seebeck coefficient in the PEDOT:PSS and g-C3N4 composite is due to reduced carrier concentration and energy filtering at the interfaces. The enhancement in electrical conductivity and the Seebeck coefficient after adding CNTs is attributed to the formation of conductive networks, increased mobility, and energy filtering at the interfaces between PEDOT:PSS and CNTs. The study suggests that combining g-C3N4 nanosheets and CNTs with PEDOT:PSS could enhance the thermoelectric performance of PEDOT:PSS-based materials.

Enhanced thermoelectric properties of Ag2Se by manipulation in carrier concentration via acetylene carbon black nanocomposites

Pristine Ag2Se has inherent limitations in its Seebeck coefficient and electronic thermal conductivity, necessitating improvements through carrier concentration manipulation. While its porous structure has been utilized to reduce carrier concentrations, achieving optimal values remains challenging. This study explores enhancing Ag2Se with acetylene carbon black (ACB) nanocomposites to further reduce carrier concentrations and improve thermoelectric (TE) properties. ACB, a cost-effective alternative to other carbon materials, has demonstrated potential in enhancing TE performance in various composites. Ag2Se and ACB composites were synthesized by dispersing different ACB weights in a solution, followed by sintering. Characterization using x-ray diffraction (XRD), Transmission and scanning electron microscopy (TEM and SEM), and other techniques confirmed the phase, structure, and morphology of the composites. The addition of ACB resulted in decreased electrical conductivity and increased Seebeck coefficient in Ag2Se, particularly at ACB concentrations up to 5.0 wt%, balancing the power factor (PF). The total thermal conductivity decreased due to mainly reduced electronic thermal conductivity. The 5.0 wt% ACB sample achieved a zT of approximately 0.8 at 383 K, comparable to the performance of composites using more expensive low-dimensional carbon materials.

Optimization of Thermoelectric Properties and Physical Mechanisms of Cu2Se-Based Thin Films via Heat Treatment.

Cu2Se is an attractive thermoelectric material due to its layered structure, low cost, environmental compatibility, and non-toxicity. These traits make it a promising replacement for conventional thermoelectric materials in large-scale applications. This study focuses on preparing Cu2Se flexible thin films through in situ magnetron sputtering technology while carefully optimizing key preparation parameters, and explores the physical mechanism of thermoelectric property enhancement, especially the power factor. The films are deposited onto flexible polyimide substrates. Experimental findings demonstrate that films grown at a base temperature of 200 °C exhibit favorable performance. Furthermore, annealing heat treatment effectively regulates the Cu element content in the film samples, which reduces carrier concentration and enhances the Seebeck coefficient, ultimately improving the power factor of the materials. Compared to the unannealed samples, the sample annealed at 300 °C exhibited a significant increase in room temperature Seebeck coefficient, rising from 9.13 μVK-1 to 26.73 μVK-1. Concurrently, the power factor improved from 0.33 μWcm-1K-2 to 1.43 μWcm-1K-2.

The Conductance and Thermopower Behavior of Pendent Trans-Coordinated Palladium(II) Complexes in Single-Molecule Junctions.

The present work provides insight into the effect of connectivity within isomeric 1,2-bis(2-pyridylethynyl)benzene (bpb) palladium complexes on their electron transmission properties within gold|single-molecule|gold junctions. The ligands 2,2'-((4,5-bis(hexyloxy)-1,2-phenylene)bis(ethyne-2,1-diyl))bis(4-(methylthio)pyridine) (Lm ) and 6,6'-((4,5-bis(hexyloxy)-1,2-phenylene)bis(ethyne-2,1-diyl))bis(3-(methylthio)pyridine) (Lp ) were synthesized and coordinated with PdCl2 to give the trans-Pd(Lmorp )Cl2 complexes. X-ray photoelectron spectroscopy (XPS) measurements shed light on the contacting modes of the molecules in the junctions. A combination of scanning tunneling microscopy-break junction (STM-BJ) measurements and density functional theory (DFT) calculations demonstrate that the typical lower conductance of meta- compared with para-connected isomers in a molecular junction was suppressed upon metal coordination. Simultaneously there was a modest increase in both conductance and Seebeck coefficient due to the contraction of the HOMO-LUMO gap upon metal coordination. It is shown that the low Seebeck coefficient is primarily a consequence of how the resonances shift relative to the Fermi energy.

Enhanced Thermoelectric Performance in Vacancy-Filling Heuslers due to Kondo-Like Effect.

To improve thermoelectric efficiency, various tactics have been employed with considerable success to decouple intertwined material attributes. However, the integration of magnetism, derived from the unique spin characteristic that other methods cannot replicate, has been comparatively underexplored and presents an ongoing intellectual challenge. A previous research has shown that vacancy-filling Heuslers offer a highly adaptable framework for modulating thermoelectric properties. Here, it is demonstrated how intrinsic magnetic-electrical-thermal coupling can enhance the thermoelectric performance of vacancy-filling Heusler alloys. The materials, Nb0.75Ti0.25FeCrxSb with 0 ≤ x ≤ 0.1, feature a fraction of magnetic Cr ions that randomly occupy the vacancy sites of the Nb0.75Ti0.25FeSb half-Heusler matrix. These alloys achieve a remarkable thermoelectric figure of merit (zT) of 1.21 at 973 K, owing to increased Seebeck coefficient and decreased thermal conductivity. The mechanism is primarily due to the introduction of magnetism, which increases the density-of-states effective mass (reaching levels up to 15 times that of a free electron's mass) and simultaneously reduces the electronic thermal conductivity. Mass and strain-field fluctuations further reduce the lattice thermal conductivity. Even higher zT values can potentially be achieved by carefully balancing electron mobility and effective mass. This work underscores the substantial prospects for exploiting magnetic-electrical-thermal synergies in cutting-edge thermoelectric materials.

High In-Plane Thermoelectric Performance of Layered Bi4O4SeCl2.

The van der Waals semiconductor Bi4O4SeCl2 has recently attracted great interest due to its extremely small lattice thermal conductivity, which may find possible application in the field of energy conversion. Herein, we accurately predict the thermoelectric transport properties of Bi4O4SeCl2 using first-principles calculations and Boltzmann transport theory, where the carrier relaxation time is obtained by fully considering the electron-phonon coupling. It is found that a maximum p-type ZT value of 3.1 can be reached at 1100 K along the in-plane direction, which originates from increased Seebeck coefficient induced by multivalley band structure, as well as enhanced electrical conductivity caused by relatively stronger intralayer bonding. Besides, it is interesting to note that comparable p- and n-type ZT values can be realized in certain temperature regions, which is very desirable in the fabrication of thermoelectric modules.

Exceptional figure of merit achieved in boron-dispersed GeTe-based thermoelectric composites

GeTe is a promising p-type material with increasingly enhanced thermoelectric properties reported in recent years, demonstrating its superiority for mid-temperature applications. In this work, the thermoelectric performance of GeTe is improved by a facile composite approach. We find that incorporating a small amount of boron particles into the Bi-doped GeTe leads to significant enhancement in power factor and simultaneous reduction in thermal conductivity, through which the synergistic modulation of electrical and thermal transport properties is realized. The thermal mismatch between the boron particles and the matrix induces high-density dislocations that effectively scatter the mid-frequency phonons, accounting for a minimum lattice thermal conductivity of 0.43 Wm−1K−1 at 613 K. Furthermore, the presence of boron/GeTe interfaces modifies the interfacial potential barriers, resulting in increased Seebeck coefficient and hence enhanced power factor (25.4 μWcm−1K−2 at 300 K). Consequently, we obtain a maximum figure of merit Zmax of 4.0 × 10−3 K−1 at 613 K in the GeTe-based composites, which is the record-high value in GeTe-based thermoelectric materials and also superior to most of thermoelectric systems for mid-temperature applications. This work provides an effective way to further enhance the performance of GeTe-based thermoelectrics.

Structural, mechanical, electronic, magnetic, optical, and thermoelectric properties of a new equiatomic quaternary heusler compound FeZrCrZ (Z = Si, Ge, Sn): A first-principles investigation

In this investigation, we undertake an ab initio exploration of the structural, mechanical, electronic, magnetic, optical, and thermoelectric characteristics of equiatomic quaternary Heusler compounds (EQH), specifically FeZrCrZ (Z = Si, Ge, Sn). Our investigation involves the utilization of the full-potential linearized augmented plane wave method (FP-LAPW) in density functional theory (DFT) framework, employing the generalized gradient approximation (GGA). The findings reveal that the Y-type-I arrangement, demonstrating ferromagnetic alignment, emerges as the most thermodynamically favored configuration among all FeZrCrZ (Z = Si, Ge, and Sn) compounds. Computed values for formation energy substantiate the feasibility of experimental synthesis.Furthermore, we meticulously determine elastic constants, confirming the structural robustness of the quaternary compounds. Dynamic stability analysis reinforces their stability. Electronic property assessments unveil the semi-metallic nature of FeZrCrZ (Z = Si, Ge, and Sn) alloys, showcasing complete spin polarization at the Fermi energy (100 %), a minimal energy gap, and magnetic moments of 2 μB when Z = Si, Ge, and 4 μB when Z = Sn. Optical property calculations encompass complex refractive index, dielectric function, reflectivity, absorption coefficient, and optical conductivity, indicating potential suitability of these compounds for optoelectronic applications. Employing Boltzmann transport theory, we investigate the thermoelectric performance of the compounds concerning temperature, and chemical potential. Evaluation of the thermoelectric response underscores their viability as thermoelectric materials, linked to a substantial figure of merit, increased Seebeck coefficient, and diminished thermal conductivity. This study provides crucial theoretical insights for experimental researchers, offering valuable information for the synthesis and application of these compounds in spintronics, thermoelasticity, and optoelectronics.

Synthesis and characterization of nanostructured tetrahedrite and its composite with dielectric inclusions

The nanostructured Cu–Sb–S materials have been synthesized by a low-cost and versatile polyol technique in a triethylene glycol medium at different temperatures (Ts = 473–533 K). The content of tetrahedrite (Cu12Sb4S13), skinnerite (Cu3SbS3), famatinite (Cu3SbS4), and chalcostibite (CuSbS2) phases was quantitatively determined via the Rietveld refinement of X-ray diffraction (XRD) patterns which showed that Cu–Sb–S pellets densified from powders synthesized at 493 K possess the highest content of tetrahedrite (i.e., ∼96.6 vol%) with small amount of skinnerite (i.e., ∼3.4 vol%). The inclusion of dielectric polyvinylpyrrolidone (PVP) up to 2.5 wt.% to tetrahedrite phase induced the alteration of structural (unit cell parameter a and volume Vunit) and microstructural (sizes of coherent scattering domains L, levels of microdeformations lε, microstresses lσ, and density of dislocations dρ) parameters. The change in the microstructure of Cu12Sb4S13-PVP composites caused the decrease of electronic thermal conductivity κe by 3 times. The increase of Seebeck coefficient (S) resulted in a power factor (PF) of (100–180) μV/K at (300–473) K for Cu12Sb4S13-PVP composite. The presented approach proves the effectiveness of the tuning thermoelectric characteristics of tetrahedrite via admixing with dielectric inclusions.

Enhanced thermoelectric performance of MoSe2 under high pressure and high temperature by suppressing bipolar effect

The electrical transport property of layered MoSe2 has a strong response to high pressure by enhancing the inter-layer interaction. However, the narrowed bandgap under high pressure will cause the bipolar effect (i.e., the thermally excited minority carriers contribute to a Seebeck coefficient with the opposite sign to the majority carriers) at high temperatures to degrade the thermoelectric (TE) performance. Hence, suppressing the bipolar effect is important to optimize the TE performance of MoSe2 under high pressure and high temperature (HPHT). In this study, the degradation of TE performance caused by the bipolar effect under HPHT in MoSe2 is investigated. It is found that in MoSe2, the electrical conductivity was improved significantly by pressure; however, the bipolar effect led to a significantly degraded Seebeck coefficient at high temperatures. By injecting massive carriers beforehand, the bipolar effect was suppressed to make a dominant type of p-type charge carries, achieving an increased Seebeck coefficient with increasing temperature, resulting in an improved power factor from 29.3 μW m−1 K−2 in MoSe2 to 285.7 μW m−1 K−2 in Mo0.98Nb0.02Se2 at 5.5 GPa, 1110 K. Combined with the reduced thermal conductivity by point defect scattering on phonons, a maximum ZT value of 0.11 at 5.5 GPa, 1110 K. This work highlights the significance of suppressing the bipolar effect under HPHT for optimizing TE performance in such layered semiconductors.

Effect of HPHT technology and Se doping on thermoelectric properties of In filled Fe doped CoSb3 materials

Skutterudite (CoSb3) is a kind of promising environment-friendly medium-temperature thermoelectric material. Indium-filled CoSb3 has been widely studied, but its bipolar effect, which is commonly generated between 600 and 700 K, seriously hinders the increase of Seebeck coefficient and zT value. The zT value not only directly reflects the overall thermoelectric performance of the material, but also reflects the thermoelectric conversion efficiency of the device. In this work, In filled and Fe, Se double doped CoSb3 materials were successfully prepared by high-temperature and high-pressure synthesis method (HPHT), with a significant shorten synthesis time of 30 mins for each sample. This research has shown that after Se doping via HPHT synthesis method, the bipolar effect of In-filled CoSb3 was significantly suppressed, thus the temperature limitations of electrical transport performance has been overcome. Through the further microstructure analysis, it was found that the crystal structure of sample In0.5Fe0.01Co3.99Sb11.91Se0.09 has the characteristics of multiple grain sizes and complex defect types. And these two microscopic morphological characteristics resulted in the sample obtaining a minimum lattice thermal conductivity of 0.94 Wm−1K−1 at a test temperature of 773.15 K. Through synergistic optimization of synthesis methods and element substitution, the maximum zT value of 1.21 of the sample In0.5Fe0.01Co3.99Sb11.91Se0.09 has been found at 773.15 K.

Improved thermoelectric properties in solid state microwave of Zn1-xYbxSb compound by Yb for Zn substitution

In this research, the Zn-Yb-Sb materials in the form Zn1-xYbxSb; x = 0.02 to 0.8, were composed by a solid-state microwave method. These samples were examined to determine the crystal structure by XRD analysis, which indexed to the orthorhombic phase. The dominant peak (112) had a clearly shift in Bragg angle from 28.536° to 28.784° with increasing Yb content. The Yb content (x) effects on the thermoelectric properties (TE) was measured at the temperature reach to 500 K. Increased the Yb content (the sample with x = 0.8) in Zn1-xYbxSb caused an increase in the Seebeck coefficient (486 μV/K at 433 K) and a decrease in each of the hole concentration (3.02 × 1021 cm−3) and the electrical conductivity (5320 S/m). Ascribing to the increased Seebeck coefficient, the higher value of the power factor measured in this research was 1257 μW/mK2 at 473K for the sample of Zn0.92Yb0.08Sb (x = 0.08).). These experimental results suggest that a clear idea of the application of the Zn1-xYbxSb for TE modules.

Uniformity of Thermoelectric Properties of N-type Bi<sub>2</sub>Te<sub>3-y</sub>Se<sub>y</sub> Bulky Compacts

Because n-type Bi<sub>2</sub>Te<sub>3</sub>-based materials exhibit lower thermoelectric performance than p-type materials and because their thermoelectric properties are sensitively changed by the composition and carrier concentration, optimizing these aspects in n-type materials is necessary to improve the thermoelectric figure of merit (ZT). In this study, the thermoelectric performance of n-type Bi<sub>2</sub>Te<sub>3</sub>-based materials was improved by reducing thermal conductivity through the formation of a Bi<sub>2</sub>Te<sub>3</sub>-Bi<sub>2</sub>Se<sub>3</sub> solid solution, Bi<sub>2</sub>Te<sub>3-y</sub>Se<sub>y</sub> and optimizing the carrier concentration through doping. As the amount of Se increased in Bi<sub>2</sub>Te<sub>3-y</sub>Se<sub>y</sub>, the carrier concentration decreased, resulting in decreased electrical and thermal conductivities and increased Seebeck coefficients. As a result, Bi<sub>2</sub>Te<sub>2.85</sub>Se<sub>0.15</sub> exhibited ZT = 0.56 at 323 K, and Bi<sub>2</sub>Te<sub>2.4</sub>Se<sub>0.6</sub> exhibited ZT = 0.60 at 423 K. Among the Bi<sub>2</sub>Te<sub>3-y</sub>Se<sub>y</sub> solid solutions, the doping effect was investigated for Bi<sub>2</sub>Te<sub>2.85</sub>Se<sub>0.15</sub> and Bi<sub>2</sub>Te<sub>2.7</sub>Se<sub>0.3</sub>, which recorded excellent thermoelectric performance at low temperatures. When halogen element (I) was doped, the power factor improved owing to the increase in carrier concentration, and the thermal conductivity decreased. As a result, the ZT values were greatly enhanced to ZT = 0.90 at 423 K for Bi<sub>2</sub>Te<sub>2.85</sub>Se<sub>0.15</sub>:I<sub>0.005</sub> and ZT = 1.13 at 423 K for Bi<sub>2</sub>Te<sub>2.7</sub>Se<sub>0.3</sub>:I<sub>0.0075</sub>. When the transition elements (Cu and Ag) were doped, the power factor was improved by the increase in Seebeck coefficient, and thereby Bi<sub>2</sub>Te<sub>2.85</sub>Se<sub>0.15</sub>:Ag<sub>0.01</sub> and Bi<sub>2</sub>Te<sub>2.85</sub>Se<sub>0.15</sub>:Ag<sub>0.01</sub> exhibited ZT = 0.76 and ZT = 0.75 at 323 K, respectively, and Bi<sub>2</sub>Te<sub>2.7</sub>Se<sub>0.3</sub>:Cu<sub>0.01</sub> exhibited ZT = 0.73 at 423 K. Conversely, doping with other transition elements (Ni and Zn), as well as group-III (Al and In) and group-IV (Ge and Sn) elements, resulted in power factors and thermal conductivities that were similar to or slightly less than those of undoped Bi<sub>2</sub>Te<sub>2.85</sub>Se<sub>0.15</sub>, leading to minimal or no improvement in ZT. Next, n-type Bi<sub>2</sub>Te<sub>2.85</sub>Se<sub>0.15</sub>:I<sub>0.005</sub> and Bi<sub>2</sub>Te<sub>2.7</sub>Se<sub>0.3</sub>:I<sub>0.0075</sub>, which exhibited the best thermoelectric performances, were fabricated as bulky compacts, and the uniformity of their thermoelectric properties were evaluated.

Re-optimising the thermoelectric properties of BiTeSe by CuO doping: From zone-melting ingots to powder metallurgy bulks with a large size

The Bi2Te3-based thermoelectric crystal ingots produced by the zone-melting (ZM) are the most widely used commercially at present. However, the poor mechanical properties caused by the ZM are unfavorable to the production of miniature devices. The mechanical properties can be improved by the powder metallurgy (PM), but the PM results in performance degradation of n-type Bi2Te3-based alloys, which could be attributed to the disappearance of intrinsic anisotropy and the increased carrier concentration originated from the “donor-like” effect of grain boundary. In this paper, the Bi2Te2.7Se0.3 + 4 wt% Te (BTST) powder was from the ground ZM ingots, and the influence of CuO doping on the thermoelectric properties of hot-pressed BTST polycrystalline bulks with a large size was investigated. It can be found that the thermoelectric properties of BTST are improved remarkably by CuO doping due to the increased Seebeck coefficient and suppressed thermal conductivity, which is caused by the synthetic effects of optimised carrier concentration, increased effective mass, and enhanced phonon scattering by the Cu2Te/Bi2Te2.7Se0.3 hetero-interfaces. Finally, the dimensionless thermoelectric figure of merit (ZT) of the sample (CuO)0.1(Bi2Te2.7Se0.3 + 4 wt% Te) reaches 1.32 at 408 K, which is about 65 % higher than that of the pristine BTST, and its average ZTave value reaches 1.27 in the temperature range of 300–473 K. The large size bulks produced by this method are not only commercialized directly, but also avoid the problem of poor mechanical properties.

Grain boundary, electrical transport and thermoelectric properties of the ultra-high rGO amount of C12A7-rGO composites

The Ca12Al14O33 ceramic (C12A7) and reduced graphene oxide (rGO) composite which an ultra-high amount (i.e., 40, 50, 60, and 70 wt%) of rGO (ultra-high amount C12A7/rGO composite) were synthesized by a solid-state reaction process. After the hydraulic press, the heat treatment in the temperature range of 773 K under the argon environment had been performed with the composite pellets for 30 min. XRD results of the C12A7 and all the ultra-high amount C12A7/rGO composites indicated a pure phase of C12A7 ceramic. Raman spectra confirmed the existence of rGO content in all the ultra-high amount C12A7/rGO composites. Raman peaks also suggested reduction of the free O22− and O2− ions from the framework of the ultra-high amount C12A7/rGO composites. SEM image presented the homogeneous grain boundary interface after the heat treatment at 773 K of the C12A7 wrapped by the rGO sheet, the agglomerated rGO sheet, and the rough interface stack of rGO sheets. UV-VIS spectroscopy presented the absorption behavior, direct energy gap, and indirect energy gap modifications of the ultra-high amount C12A7/rGO composites. Electrical conductivity of the ultra-high amount C12A7/rGO composites illustrated larger than 108 times improvement with temperature independence. Range of −5 to −17 μV/K , temperature dependence, and increased with rGO content increasing Seebeck coefficient were reported. Thermal conductivity of the ultra-high amount C12A7/rGO composites was increased with the rGO content increasing. Both the Power factor (PF) and the figure of merit (ZT) of the ultra-high amount C12A7/rGO composites were temperature dependent and were increased with the rGO content increasing, within the range of 0.4 μW/m.K2 of PF and the range of 3x10−4 of ZT, respectively. These experimental results verified grain boundary, modified energy band, electrical transport properties and thermoelectric properties of C12A7/rGO composites loading with ultra-high content rGO

Synthesis, Characterization and Power Factor Estimation of SnSe Thin Film for Energy Harvesting Applications

In this work, a simple, cost-effective successive ionic layer adsorption and reaction (SILAR) deposition technique has been used to deposit a high-quality tin selenide (SnSe) thin film onto a glass substrate. Structural, morphologic, and thermoelectric properties have been characterized for the prepared thin film. X-ray diffraction (XRD) results of the SnSe thin film reveal an orthorhombic structure phase. The morphological properties of the prepared thin films have been studied using field emission scanning electron microscopy (FESEM). The stoichiometric composition of the deposited thin film and the elemental binding energies of the Sn and Se elements have been investigated with energy-dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The Fourier transformation infrared (FTIR) spectrum of the SnSe thin film displays vibrational modes of chalcogenides bonds. These results suggest that the developed thin film is crystalline, uniform, and without impurities and is appropriate for energy harvesting applications. The prepared thin film’s Seebeck coefficient and electrical resistivity were estimated through ZEM-3 from room temperature to 600 K. The power factor was evaluated. A substantially high electrical conductivity is observed, which decreases somewhat with temperature, suggesting a semimetal conducting transport—the absolute values of the Seebeck coefficient increase with temperature. The resulting power factor showed the highest values near room temperature and a somewhat decreasing trend as the temperature increased. Despite lower values of the Seebeck coefficient, the substantially enhanced power factor is due to the higher electrical conductivity of the thin film, superior to that reported previously. This precursor study demonstrates promising results for developing high-performance flexible thermoelectric devices via a simple and facile SILAR strategy.

Enhancing Strategy of the Small-Polaron Conductivity in LaCrO3: First-Principles Calculations and Experimental Validation.

LaCrO3 (LCO) has promising applications as a p-type conductive material in the fields of transparent conducting oxes, high-temperature sensors, and magnetohydrodynamic power generators. However, the easy volatility of the Cr element, along with the issues of low electrical conductivity caused by the small-polaron conduction mechanism and wide band gap, has hindered the widespread application of LCO. In this work, based on band engineering and defect engineering, we screened doping schemes through first-principles calculations that can reduce Cr volatility by enhancing the Cr-O bond energy. We also aimed to promote small-polaron hopping and improve the electrical conductivity by introducing impurity levels. Additionally, we conducted a thorough analysis of the small-polaron conductivity mechanism. Through the solid-state method, we successfully prepared codoped LCO with Ca and Zn. The Zn dopants effectively enhanced the Cr-O bond strength, suppressed the Cr volatility, and improved high-temperature stability. The Zn dopants introduced additional impurity energy levels within the band gap, significantly changing the mobility of small polarons. Through optimal doping concentration, the La0.7Ca0.3Cr0.95Zn0.05O3 sample demonstrated a significant enhancement in electrical conductivity compared to La0.7Ca0.3CrO3, increasing from 7 to 60 at 1000 K. Additionally, the impurity energy levels enhanced the asymmetry near the Fermi level, resulting in an increased Seebeck coefficient (S). This is beneficial for the production of high-temperature sensors. The output voltage of an LCO thermocouple module reaches up to 58 mV at 2170 K, indicating that the performance optimization strategy employed in this work has significant implications for the regulation and application of oxide electrical materials.

High thermoelectric performance of GeTe-MnTe alloy driven by spin degree of freedom

GeTe has been known as an excellent thermoelectrics, whereas its realistically application is limited by its structural phase transition near 700 K. Here, we show that the temperature of phase transition can be suppressed below 300 K by alloying 35% MnTe. The GeTe-MnTe alloy exhibits the much different transport properties from GeTe. Its room-temperature Seebeck coefficient is close to that of optimized GeTe, while its carrier concentration is one order higher. The increase of Seebeck coefficient of GeTe-MnTe is found to be accompanied with the decrease of magnetic susceptibility, while GeTe shows the opposite trend. By optimizing the carrier concentration with Bi doping and Bi/Sb co-doping, the peak figure of merit of GeTe-MnTe reaches 1.46 at 823 K. Our study reveals that GeTe-MnTe alloy is a novel and promising thermoelectric material.