Thermoelectric Figure Of Merit Research Articles

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

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

Exploring superconductivity, supercapacitance and thermoelectric properties of NbCr[formula omitted] and its alloys with Li and Mg: A first-principles Investigation

In the present study, the superconductivity, supercapacitance, and thermoelectric properties of the NbCr2 and its alloys with Li and Mg (with alloy composition of x=0.5 in replacement with Cr atoms) have been surveyed using density functional theory. The mechanical, thermodynamic, and dynamic stability of the pure and alloy compositions have been checked by the results of the cohesive energy, enthalpy of formation energy, and phonon density of states. Moreover, the largest value of the critical temperature (Tc) which has been achieved belongs to the pure NbCr2 with a value of 13.76 K. In addition, the largest values of Tc for Li and Mg alloys are 11.83 and 3.42 K, respectively. Furthermore, the largest peak of the quantum capacitance at room temperature and as a function of the applied voltage is also related to the pure NbCr2 with a value of 676.77 μF/cm2 at the voltage of −1.86 V. In addition, the largest value of the surface charge storage occurred at the negative bias of −1.88 V with a value of −1261.27 μC/cm2. For thermoelectric properties, the largest peak of the thermoelectric power factor per relaxation time as a function of chemical potential and at room temperature belongs to Li alloy with a value 20.03 × 1016μW/(m K2 s) at the negative chemical potentials of −0.73 eV. The largest value of electronic thermal conductivity per relaxation time belongs the Li alloy at 500 K with a value of 48.71 × 1014 W/(m K s) and the largest value of lattice thermal conductivity is also related to Li alloy with the value of 22.8 W/(m K) at 100 K. All of these results represent the materials which not only have the superconductivity property but also supercapacitance and thermoelectric properties that could be useful as electrode materials in the energy storage industries.

Unusual Electrical Conductivity Enhancement in Stable n-Type Carbon Nanotube Networks.

Organic molecule-doped n-type single-walled carbon nanotube (SWCNT) networks are promising candidates for advanced energy applications, such as flexible thermoelectrics and photovoltaics. Yet charge transport in n-type SWCNTs is limited by two factors: i) charge localization impeding inter-tube transport caused by disordered mesostructure of randomly oriented SWCNTs and ii) reduction of charge carrier concentration driven by oxidation. Herein, studied the relationship between the mesostructure and thermoelectric properties of n-type SWCNTs obtained by surfactant-functionalization and polymer-dopant grafting. Surprisingly, the electrical conductivity of the polymer-doped SWCNTs keeps increasing with increasing polymer content, even after the saturation of carrier concentration, resulting in 12x higher conductivity on polymer-doping compared to surfactant-functionalization. While hopping transport typically dominates in disordered systems, it is shown that a bridging effect from the polymer causes unusual band-like conduction in polymer-doped SWCNTs. Additionally, since surfactants are essential to prevent oxidation and retain n-type over a long duration, shows that SWCNTs obtained through a dual-functionalization strategy using both polymer-dopant and surfactant, demonstrates a long-term stable high n-type thermoelectric power factor, when the surfactant amount is carefully controlled. Besides thermoelectrics, the findings are of general interest to developing stable and conductive n-type SWCNTs for various energy and electronic applications.

A novel characteristic curve for thermoelectric cooler application in realistic thermal circumstances: Theory and experiment

On the materials level, the performance of thermoelectric (TE) devices can be defined by the thermoelectric figure of merit (zT). This, however, does not provide a complete picture due to the complex interplay between electronic and thermal transport properties and the uncertain thermal impedance matching between external and internal thermal resistances in different realistic thermal circumstances. Appropriate design of individual material properties and geometry parameters considering the realistic thermal circumstance can greatly enhance the device-level performance of TE devices. In this work, we develop a framework to clarify such interactions in thermoelectric coolers (TEC) with a newly proposed q-h characteristic curve, which can be used to identify how a TEC design is of effectiveness for a specific realistic thermal circumstance. The effects of zT, the individual TE material properties (i.e., thermal conductivity k, electrical conductivity σ and Seebeck coefficient S) as well as the geometry parameters (i.e., pillar height and filling factor) on the q-h characteristic curve are theoretically and experimentally investigated, respectively. TEC modules with higher zT, short pillars and high filling factor show stronger capability to handle high heat flux load, especially for the cases with high heat dissipation coefficient at hot side. The thermal property (k) and electrical properties (σ and S) are responsible for the low heat flux load (e.g., wearable TEC) and high heat flux load (e.g., on-chip TEC cooling), respectively. For wearable TEC, increasing the internal thermal resistance can prevent the back flow heat, which can be achieved with tall pillars, low filling factor and optimizing zT towards lowering thermal conductivity k. For on-chip TEC cooling, reducing the Joule heating and increasing the thermoelectric effect become dominant factors in lowering the code-side temperature of TEC modules. This can be achieved with short pillars, high filling factor and optimizing zT towards increasing the power factor S2σ. This work provides significant insights into the complex interplay between material-level properties, device-level parameters and the external thermal circumstance in determining the performance of TEC devices. The results enable researchers to design optimal TEC devices for realistic applications with different boundary conditions.

Approaching crystal’s limit of thermoelectrics by nano-sintering-aid at grain boundaries

Grain boundary plays a vital role in thermoelectric transports, leading to distinct properties between single crystals and polycrystals. Manipulating the grain boundary to realize good thermoelectric properties in polycrystals similar as those of single crystals is a long-standing task, but it is quite challenging. Herein, we develop a liquid-phase sintering strategy to successfully introduce Mg2Cu nano-sintering-aid into the grain boundaries of Mg3(Bi, Sb)2-based materials. The nano-aid helps to enlarge the average grain size to 23.7 μm and effectively scatter phonons, leading to excellent electrical transports similar as those of single crystals and ultralow lattice thermal conductivity as well as exceptional thermoelectric figure of merit (1.5 at 500 K) and conversion efficiency (7.4% under temperature difference of 207 K). This work provides a simple but effective strategy for the fabrication of high-performance polycrystals for large-scale applications.

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

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

Enhancing thermoelectric properties of spinel ZnFe2O4 by Ni substitution through electron hopping mechanism

The prime goal of this novel work is to investigate the efficacy of spinel zinc ferrite as a thermoelectric material and its performance enhancement for high temperature applications. Zn1-xNixFe2O4 (0 ≤ x ≤ 0.2) were prepared by sol-gel method and their structural, morphological, and thermoelectric behaviours were examined as functions of composition and temperature. Among the studied compositions, Zn0.8Ni0.2Fe2O4 exhibits the highest electrical conductivity (σ) of 49.83 S/m, the largest power factor of 6.66 μW/mK2, and the lowest thermal conductivity (κ) of 0.36 W/mK at 947 K, thus extending to an overall enhancement in the thermoelectric figure of merit (zT). Conduction through electron hopping is proven to be the main driving force for the enhancement in electrical and thus thermoelectric properties. Results reveal that thermoelectric properties of ZnFe2O4 can potentially be enhanced by the doping Ni at Zn site and opens up an exciting opportunity for the utilization of this spinel ferrite as a novel thermoelectric material for applications involving elevated temperatures.

Research of the impact of uniaxial tension on the thermoelectric properties of NbCoX (X=Ge, Sn, Pb) compounds

Half-Heusler materials have been confirmed as excellent thermoelectric materials. To simulate the stress conditions in engineering applications, we adopt uniaxial tensile strain to assess the impact of lattice changes on NbCoX (X=Ge, Sn, Pb) compound's thermoelectric performance. The research reveals that when NbCoX compounds are stretched by 1.5 %, the material almost does not decrease the power factor but significantly reduces thermal conductivity, thereby enhancing the ZT value. At a carrier concentration of 1E22 cm−3 and a temperature of 873 K, the predicted ZT values for p-type NbCoSn compound reach 0.359 and 0.354 after stretching by 1.5 % in the x-y and z directions, respectively. Compared to the previous original values, this improvement is approximately 1.5 times, highlighting the significant role of tensile strain in enhancing thermoelectric performance. This may be attributed to changes in compound lattice symmetry induced by strain, leading to increased defects and interfaces, which complicate phonon transport paths, resulting in a decrease in the average phonon mean free path and consequently lowering thermal conductivity. Additionally, with the increase in atomic number of Ge, Sn, and Pb, their thermoelectric figure of merit also increases continuously, with ZT values remaining higher under stretching than compression. Such research provides a new avenue for designing and optimizing high-performance thermoelectric materials and offers insights into strain engineering for future exploration of thermoelectric materials.

Effect of single and dual doping on the thermoelectric properties of FeVSb0.95Sn0.05 and Fe0.95Co0.05VSb0.90Sn0.10 half-Heusler alloys

FeVSb in addition to a set of novel FeVSb0.95Sn0.05 and Fe0.95Co0.05VSb0.90Sn0.10 half-Heusler alloys were fabricated by arc melting followed by induction melting simple methods. Impacts of single Sn-doping and double Co- and Sn-doping on the structural and thermoelectric properties of FeVSb were investigated in this article. Structural and thermoelectric properties of FeVSb, FeVSb0.95Sn0.05 and Fe0.95Co0.05VSb0.90Sn0.10 compounds have been extensively studied in this work. N-type conduction was confirmed for the FeVSb system and for the doped FeVSb0.95Sn0.05 and Fe0.95Co0.05VSb0.90Sn0.10 alloys. The absolute value of Seebeck coefficient for the single Sn-doped sample increased from 127 μV/K to 155 μV/K, with the temperature increasing. Similarly, the Seebeck coefficient of the double Co- and Sn-doped alloy also increased from 40 μV/K to 60 μV/K. The thermoelectric power factor was notably enhanced for the dual doped Fe0.95Co0.05VSb0.90Sn0.10 alloy reaching 14 μW/cm.K2. Lattice thermal conductivity of the single Sn-doped FeVSb0.95Sn0.05 alloy decreased considerably over the whole temperature range. A maximum zT of 0.084 was achieved for FeVSb0.95Sn0.05 alloy at 575 K. The improved figure of merit due to doping is attributed to the phonon scattering at point defects. Sn-doping has significantly reduced thermal conductivity due to the enhanced point-defect and electron–phonon scatterings which contributed to improved thermoelectric figure of merit. Our findings showed also that the room-temperature thermal conductivity is seriously reduced via Sn and Co dual doping leading to higher ZT value for Fe0.95Co0.05VSb0.90Sn0.10 alloy. Promising candidates for further thermoelectric applications could be achieved by Sn-doping and double Co- and Sn-doping.

Insight into phase stability and thermoelectric properties of semiconducting iron silicides with manganese substitution: β-Fe1−xMnxSi2 (0≤x≤0.05)

Metal-doped iron silicides (β-FeSi2) are promising thermoelectric materials for high-temperature applications. However, the addition of metal dopants usually causes the formation of secondary metallic phases, resulting in the degradation of thermopower. Here we report the stability of semiconducting β-phase (higher than 95 %) of Mn-doped β-FeSi2 obtained at Mn concentration from 1 % to 5 %, where the samples were prepared through direct arc melting and heat treatment process. The carrier density remarkably increases with Mn content, but the mobility decreases. The electrical resistivity significantly decreases with Mn content. The Seebeck coefficient of Mn-doped samples is improved and stable at high-temperature regions because of the reduction of the bipolar effect and β-phase stability. The thermal conductivity slightly increases with Mn. As a result, the maximum thermoelectric power factor PF = 970 μWm−1K−2 and dimensionless figure of merit ZT = 0.12 at 800 K are obtained in a 3 % Mn-doped sample. The stability of β-phase and the improved carrier density are the origins of enhanced thermoelectric properties, where the Seebeck coefficient is improved, and the electrical resistivity is reduced. Our study provides insight into the importance of phase stability for enhancing thermoelectric transport in Mn-doped β-FeSi2.

Enhancement of thermoelectric properties in Sr0.6La0.4Nb2O6-δ-based ceramics by addition of graphite

Oxide thermoelectric materials have a wide range of applications due to their excellent stability, low cost, and non-toxic properties. However, their low thermoelectric conversion efficiency limits their practical use. Therefore, improving the performance of oxide thermoelectric materials has become the focus of current research. Interface engineering is an important approach to enhance thermoelectric properties by optimizing electrical transport properties through multiphase composite regulation of phase interface structure. A series of Sr0.6La0.4Nb2O6-δ/x wt% graphite (x = 0, 0.6, 1.0, 1.5, 2.0) composite ceramics thermoelectric materials were prepared, and the mechanism for improving their thermoelectric properties was explored. Graphite serves as an electron momentum amplifier within the Sr0.6Ba0.4Nb2O6-δ matrix, thereby augmenting both conductivity and power factor values significantly. Notably, the incorporation of 1.5 wt% graphite led to a remarkable enhancement in the thermoelectric power factor at 1073 K, reaching an impressive value of 254.84 μW/K2m - representing a notable increase of approximately 51 % compared to the unmodified sample - primarily attributed to the elevated electrical conductivity.

Enhancing thermoelectric performance with perpendicular anisotropic magnetic domain arrays

In recent years, the incorporation of magnetic nanoparticles into thermoelectric materials has been introduced to enhance their performance. However, understanding the impact of dispersed magnetic substances in the matrix on thermoelectric properties, considering different domain directions, is crucial for performance improvement. In this study, we have designed and fabricated high-quality epitaxial single crystal thin films consisting of FePt arrays with varying magnetic domain directions embedded in an Sb2Te3 matrix. Our findings reveal that the electrical transport behavior of the films responds differently to magnetic materials with distinct domain directions, especially in the case of discontinuous arrays. The FePt array oriented perpendicular to the carrier flow direction effectively regulates the direction of carrier movement and local low-energy carriers, functioning as an "energy supplier" to enhance material performance. Simultaneously, the quantum dots formed between the Sb2Te3 and the metal film play the role of carrier channels, further regulating the carrier concentration. Therefore, the perpendicular magnetic anisotropy array synergistically modulates the electrical transport behavior through carriers, resulting in a significant improvement in the thermoelectric power factor. By increasing the S value at the measurement temperature, we achieved a maximum power factor (PFmax) of 3.35 mWm-1K-2 and an average power factor (PFave) of 3.14 mWm-1K-2.

Enhanced Thermoelectric Performance of N-Type PbSe Through Semi-Coherent Nanostructure by AgCuTe Alloying.

N-type PbSe thermoelectric materials encounter challenges in improving the power factor due to the single-band structure near the Fermi level, which obstructs typical band convergence. The primary strategy for enhancing the thermoelectric figureof merit (ZT) for n-type PbSe involves reducing lattice thermal conductivity (κlat) by introducing various defect structures. However, lattice mismatches resulting from internal defects within the matrix can diminish carrier mobility, thereby affecting electrical transport properties. In this study, n-type AgCuTe-alloyed PbSe systems achieve a peak ZT value of ≈1.5 at 773 K. Transmission electron microscopy reveals nanoprecipitates of Ag2Te, the room temperature second phase of AgCuTe, within the PbSe matrix. Meanwhile, a unique semi-coherent phase boundary is observed between the PbSe matrix and the Ag2Te nanoprecipitates. This semi-coherent phase interface effectively scatters low-frequency phonons while minimizing damage to carrier mobility. Additionally, the dynamic doping effect of Cu atoms from the decomposition of AgCuTe within the matrix further optimize the high-temperature thermoelectric performance. Overall, these factors significantly enhance the ZT across the whole temperature range. The ZT value of ≈1.5 indicates high competitiveness compared to the latest reported n-type PbSe materials, suggesting that these findings hold promise for advancing the development of efficient thermoelectricsystems.

Quantum confinement and energy filtering effect enhancing the thermoelectric power factor of InGaAs with buried ErAs nanoparticles

Quantum confinement and energy filtering effect enhancing the thermoelectric power factor of InGaAs with buried ErAs nanoparticles

Energy Filtering in Doping Modulated Nanoengineered Thermoelectric Materials: A Monte Carlo Simulation Approach.

Using Monte Carlo electronic transport simulations, coupled self-consistently with the Poisson equation for electrostatics, we explore the thermoelectric power factor of nanoengineered materials. These materials consist of alternating highly doped and intrinsic regions on the scale of several nanometers. This structure enables the creation of potential wells and barriers, implementing a mechanism for filtering carrier energy. Our study demonstrates that by carefully designing the nanostructure, we can significantly enhance its thermoelectric power factor compared to the original pristine material. Importantly, these enhancements stem not only from the energy filtering effect that boosts the Seebeck coefficient but also from the utilization of high-energy carriers within the wells and intrinsic barrier regions to maintain relatively high electronic conductivity. These findings can offer guidance for the design and optimization of new-generation thermoelectric materials through improvements in the power factor.

Manipulating the metal–insulator transitions and thermoelectric bi-functionality for correlated vanadium dioxide pellets

The electron correlations as triggered by on-site Coulomb repulsion within correlated vanadium dioxide (VO2) open up an emerging paradigm to explore new electronic phases and promising device applications. Apart from correlated electrical transport, the thermoelectric thermopower (S) of VO2 also undergoes abrupt variation across the critical temperature (TMIT) that sheds lights on the potential thermoelectric functionality. Nevertheless, bridging bi-functionality of VO2 associated with the thermistor and thermoelectric properties is still restricted by the limitation in improving the absolute magnitude of S and temperature coefficient of resistance (TCR). Herein, we demonstrate the widely adjustable metal–insulator transition (MIT) behavior and overlooked thermoelectric performance for Ti-substituted VO2 pellets that enable the bi-functionality strategy as combined with thermistor and thermoelectric properties. As-achieved tunable TMIT while maintaining large |TCR| is herein achieved for Ti-substituted VO2 pellets that enables practical device applications near room temperature. Apart from the well-known MIT functionality, we reveal the overlooked thermoelectric properties for VO2 via coherently co-sintering with TiO2 that introduces a new freedom (thermopower). Specifically, the largely enhanced thermopower observed for insulating V1−xTixO2 exceeds the one for pristine VO2 by five times, while the thermoelectric power factor for its metallic phase is comparable to typical organic or oxide thermoelectric materials. The presently achieved thermistor and thermoelectric bi-functionality (e.g., |S| > 100 μV/K and |TCR| > 1 K−1) for Ti-substituted VO2 pellets extends the horizons in material designs that combines such a bi-functionality to achieve both the passive and active sensing for improving the accuracy in thermal perturbations of VO2 bulk as infrared detectors near room temperature.

Capillary compression induced outstanding n-type thermoelectric power factor in CNT films towards intelligent temperature controller

One-dimensional carbon nanotubes are promising candidates for thermoelectrics because of their excellent electrical and mechanical properties. However, the large n-type power factor remains elusive in macroscopic carbon nanotubes films. Herein, we report an outstanding n-type power factor of 6.75 mW m−1 K−2 for macroscopic carbon nanotubes films with high electrical and thermal conductivity. A high-power density curl-able thermoelectric generator is fabricated with the obtained carbon nanotubes films, which exhibits a high normalized power output density of 2.75 W m−1 at a temperature difference of 85 K. The value is higher than that of previously reported flexible all-inorganic thermoelectric generators (<0.3 W m−1). An intelligent temperature controller with automated temperature-controlling ability is fabricated by assembling these thermoelectric generators, which demonstrates the potential application of the carbon nanotubes films in automated thermal management of electronic devices where requires a large thermoelectric power factor and a large thermal conductivity simultaneously.

Wedge-shape Al and Mg co-doped zinc oxide thin films: A Facile Route to achieve high thermoelectric power factor

Thin film thermoelectric technology has immense potential to become a next-generation power source for small-scale electronics. However, the rapid development of thin film thermoelectric still lacks a controllable structural design to improve the performance of thermoelectric devices for required temperature applications. This work presented a controlled thermoelectric design of ZnO-based thin films by Al and Mg co-doping using ALD. Herein, the Mg-doped ZnO sample exhibits the highest Seebeck coefficient of −311.83 μVK−1 at 500oC, while the maximum thermoelectric power factor of 3.68 μWcm−1K−2 is obtained at 300oC, which drops for higher temperatures. This decrease in power factor resulted from the reduction in electrical conductivity above 300oC. Similarly, the Al and Mg co-doped ZnO sample (Mg/Al ≈2 at%) exhibits a high thermoelectric power factor of 3.85 μWcm−1K−2 for ZnO based material due to its moderate electrical conductivity and Seebeck coefficient value at 325oC and behave monotonically for elevated temperatures. Scanning electron microscope (SEM) images show the formation of wedge-shaped structures for Al-incorporated samples, which helps to boost the overall thermoelectric performance. Additionally, we performed XRD, UV–Vis, Hall, and AFM analysis to get a deep insight into structural, optical, electrical, and surface features of the grown thin films and their linkage with the thermoelectric properties.

A Universal, Highly Stable Dopant System for Organic Semiconductors Based on Lewis-Paired Dopant Complexes.

Chemical doping of organic semiconductors is an essential enabler for applications in electronic and energy-conversion devices such as thermoelectrics. Here, Lewis-paired complexes are advanced as high-performance dopants that address all the principal drawbacks of conventional dopants in terms of limited electrical conductivity, thermal stability, and generality. The study focuses on the Lewis acid B(C6F5)3 (BCF) and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) bearing Lewis-basic -CN groups. Due to its high electron affinity, BCF:F4TCNQ dopes an exceptionally wide range of organic semiconductors, over 20 of which are investigated. Complex activation and microstructure control lead to conductivities for poly(3-hexylthiophene) (P3HT) exceeding 300 and 900 S cm-1 for isotropic and chain-oriented films, respectively, resulting in a 10 to 50 times larger thermoelectric power factor compared to those obtained with neat dopants. Moreover, BCF:F4TCNQ-doped P3HT exhibits a 3-fold higher thermal dedoping activation energy compared to that obtained with neat dopants and at least a factor of 10 better operational stability.

Significant Improvement in Thermoelectric Properties of Carbon-Reinforced Cementitious Composites Achieved by Regulating the Graphitization Degree of Expanded Graphite.

Building structures are exposed to direct sunlight for a long time, accumulating a large amount of low-grade thermal energy, which aggravates environmental pollution and energy consumption. Thermoelectric cement-based composites can realize the interconversion of thermal and electrical energy, showing great potential benefits in large-scale heat collection and energy conversion. Although a lot of exploration and research has been carried out on the thermoelectric properties of cement-based composites reinforced with carbon materials, the contribution of the characteristics of carbon materials, such as the graphitization degree, to the thermoelectric properties of cement-based composites is still unclear. In this article, the graphitization degree of expanded graphite (EG) was modulated by etching EG with an acid solution. The low graphitization degree improves the effective mass of carriers and aggravates the electron and phonon scattering at the interface of EG/cement-based composites. Low thermal conductivity was obtained while increasing the Seebeck coefficient of EG/cement-based composites. The power factor (17.1 μW m-1 K-2) and thermoelectric figure of merit (2.95 × 10-3) of the sample are increased by 18.6 times and 44.2 times, respectively, achieving the highest thermoelectric performance in cement-based composites reinforced with carbon materials. This study provides a direction for improving the thermoelectric properties of cement-based composites by structural regulation of carbon materials.