Thermoelectric Conversion Efficiency Research Articles

High density lath twins lead to high thermoelectric conversion efficiency in Bi2Te3 modules.

Thermoelectric (TE) generators based on bismuth telluride (Bi2Te3) are recognized as a credible solution for low-grade heat harvesting. In this study, an combinative doping strategy of both the donor (Ag) and the acceptor (Ga) in Ag9GaTe6 as dopants is developed to modulate the microstructure and improve the ZT value of p-type Bi0.4Sb1.6Te3. Specifically, the distribution of Ag and Ga in the matrix synergistically introduces multiple phonon scattering centers including lath twins, triple junction boundaries, and Sb-rich nanoprecipitates, leading to an obviously suppressed lattice thermal conductivity of 0.50 W m-1 K-1 at 300 K. At the same time, such unique microstructures of lath twins synergistically enhance the room-temperature power factor to 48.8 μW cm-1 K-2 and improve the Vickers hardness to 0.90 GPa. Consequently, a high ZT of 1.40 at 350 K and ZTave of 1.24 (300-500 K) are achieved in the Bi0.4Sb1.6Te3 + 0.03 wt% Ag9GaTe6 sample. Based on that, a competitive conversion efficiency of 6.5% at ΔT = 200 K is obtained in the constructed 17-couple TE module, which exhibits no significant change in the output property after 30 thermal cycle tests benefiting from the stable microstructure.

Achieving high thermoelectric conversion efficiency in Bi2Te3-based stepwise legs through bandgap tuning and chemical potential engineering.

In this study, we show that the energy conversion efficiency in thermoelectric (TE) devices can be effectively improved through simultaneous optimization of carrier concentration, bandgap tuning, and fabrication of stepwise legs. n- and p-type Bi2Te3-based materials were selected as examples for testing the proposed approach. At first, the Boltzmann transport theory was employed to predict the optimal temperature-dependent carrier concentration for high thermoelectric performance over a broad temperature range. Then, the synthesized n-Bi2Te3-xSex and p-Bi2-xSbxTe3 solid solutions were tested to evaluate their suitability for fabricating the stepwise thermoelectric legs. The output energy characteristics of the designed TE devices were estimated using numerical modeling employing the finite element method. The theoretical simulation revealed an improvement in the conversion efficiency between the best homogeneous and stepwise TE legs from 8.8% to 10.1% and from 9.9% to 10.8% in p-type and n-type legs, respectively, which is much higher than the efficiency of the industrial thermoelectric modules (3-6%). The measured conversion efficiency of the fabricated n- and p-type stepwise legs reached very high values of 9.3% and 9.0%, respectively, at the relatively small temperature gradient of 375 K. This work suggests carrier concentration and bandgap engineering accompanied by the stepwise leg approach as powerful methods for achieving high energy conversion efficiency in thermoelectric converters.

POWER FACTOR OF Bi2Te3 AND Sb2Te3 ENHANCED BY HIGH DENSITY AND HARDNESS

The power factor is an indicator of the performance of thermoelectric materials. Many researchers improved the thermoelectric conversion efficiency of materials by various techniques such as doping, substitution, and decreasing particle size for dense samples. We present Bi2Te3 and Sb2Te3 materials prepared by hot pressing method at 673 K for 2 h in Ar atmosphere. Bulk samples were investigated for their crystalline structure, hardness, and power factor by XRD, micro-Vickers hardness, and ZEM-3, respectively. The Seebeck coefficient, electrical resistivity, and power factor of n- Bi2Te3 and p- Bi2Te3 bulk samples were higher than literature data in the same temperature range of 325 to 475 K. The higher power factor value of Bi2Te3 and Bi2Te3 bulk samples of this study have resulted from the high density and high micro-Vickers hardness of the samples.

Development of Transpiration-Type Thermoelectric-Power-Generating Material Using Carbon Nanotube Composite Papers with Capillary Action and Heat of Vaporization

A transpiration-type thermoelectric-power-generating paper based on previously developed carbon nanotube (CNT) composite paper, which is a composite material of CNTs and pulp that can generate thermoelectric power, was developed. The newly developed thermoelectric-power-generating material does not require an external high-temperature heat source due to the ability of paper to absorb liquid through capillary action and heat of vaporization generated when the liquid evaporates. The aim of this study is to investigate the feasibility of realizing the transpiration-type thermoelectric-power-generating paper. To begin with, the type of paper used as raw material for the composite paper was examined, and the fabrication process was modified in order to obtain more efficient liquid absorption based on capillary action. Then, the absorbing ability of the liquid was evaluated. Next, the feasibility of thermoelectric power generation using the heat of vaporization was confirmed. Moreover, for more efficient thermoelectric conversion, multisheet structures were also studied. Through several experiments, the material’s feasibility was verified, and it was confirmed that more power can be easily obtained through the use of multiple sheets. Specifically, a single sample spontaneously generated a temperature difference of up to 1.7 °C due to the heat of vaporization, generating an electromotive force of 36 μV. From the sample with a five-sheet structure, an electromotive force of 356 μV was obtained at a temperature difference of 2 °C. This material can be used in watery environments, such as rivers, lakes, and hot springs, and is expected to become a new energy-harvesting device.

Thermal-electrical coupling analysis of the static heat pipe cooled reactor under heat pipe failure condition

Heat pipe cooled reactors have gained significant attention as a research hotspot in small nuclear reactor technology due to their miniaturization and mobility features, making them suitable for various special applications like deep-space exploration, underwater scientific research, catalog research, and distributed power supply in remote areas. This study employs COMSOL Multiphysics to analyze the heat transfer and thermoelectric conversion characteristics of a static heat pipe reactor. We investigate the thermal-electrical coupling behaviors under local heat pipe failure condition and examine its combination with the whole thermoelectric system unloading condition. Under steady-state conditions, the heat pipes exhibit isothermal properties of 112.4 °C, 114.8 °C, and 117.3 °C in the side, center, and corner channels, respectively. In the condition of local heat pipe failure, it was assumed that five adjacent heat pipes failed. Consequently, the temperature gradient of the failed heat pipe at the center channel reached 485.1 °C. Despite the local heat pipe failure, the output power of the thermoelectric system still reached 120.8 kW, and the overall thermoelectric conversion efficiency remained at 12.1 %. When considering the coupling of local heat pipe failure with the unloading condition of the thermoelectric system, the maximum temperature of the reactor core increases by 675.8 °C. Additionally, the temperature gradient in the heat pipe adiabatic section rises to 517.3 °C in the center channel. The combined effect of overall temperature increasing and thermoelectric system unloading leads to open voltages ranging from 140.0 V to 149.0 V in the thermoelectric subsystem at different ports. The research findings suggest that the system temperature rise caused by the whole system unloading condition is more significant. Thus, considering the coupling effect of thermoelectric system unloading and heat pipe failure condition is conservative and crucial for a comprehensive analysis of the system behaviors. These results contribute to the understanding and optimization of heat pipe cooled reactors for various specialized applications.

Multifunctional GeMnTe2 Synergistically Optimizes Thermoelectric Properties of SnTe-In2Te3 Alloys.

SnTe-In2Te3 alloys ensure excellent electrical properties in the whole temperature region due to the resonant level. Nevertheless, temperature-sensitive resonance states and single phonon scattering restrict further improvement of thermoelectric performance. Consequently, it is anticipated that additional electrically independent scattering sources should be introduced to impede phonon transport. Here, the SnTe-In2Te3-GeMnTe2 alloy is prepared by further solidifying cubic GeMnTe2, which demonstrates multiple modulation effects. The highly redissolved Mn2+ promotes the valence band convergence, enhances the Seebeck coefficient at higher temperature, and balances the possible weakened resonance level effect at higher carrier concentrations, and a high average power factor (1.94 mW m-1 K-2) is realized over the entire temperature range. Additionally, compensatory vacancies, substitutions, and Ge/Mn precipitates are easily constructed with GeMnTe2 alloying, leading to a further reduction in lattice thermal conductivity, which reaches κl ∼ 0.6 W m-1 K-1 at 850 K. Ultimately, a high peak zT of ∼1.25 (850 K) and a zTave of 0.72 (300-850 K) are realized in (SnTe)2.91(In2Te3)0.03(Ge0.5Mn0.5Te)1.2, and the maximum thermoelectric conversion efficiency of ∼2.8% (ΔT ∼ 450 K) is achieved. The present results indicate multiple effects of GeMnTe2 in enhancing the thermoelectric performance of SnTe-In2Te3 alloys.

Hybrid Transverse Magneto‐Thermoelectric Cooling in Artificially Tilted Multilayers

AbstractIn artificially tilted multilayers comprising two different conductors that are alternately and obliquely stacked, transverse thermoelectric conversion occurs, in which charge and heat currents are interconverted in the orthogonal direction. Although transverse thermoelectric conversion also occurs in homogeneous materials as an intrinsic transport phenomenon owing to the effects of magnetic fields, magnetization, and spins on conduction carriers, such magneto‐thermoelectric effects are investigated independently of thermoelectrics for artificially tilted multilayers. Here, this study shows that the synergy of these different principles improves the performance of transverse thermoelectric conversion. Using lock‐in thermography techniques, transverse thermoelectric conversion processes are visualized in artificially tilted multilayers and the experiments clarify how nonuniform charge currents are converted into orthogonal heat currents. Through the measurements of temperature change under magnetic fields, the contributions of the magneto‐thermoelectric effects are quantified in the artificially tilted multilayers and magnetically enhanced hybrid transverse thermoelectric cooling is demonstrated. By replacing one of the conductors in the multilayer with permanent magnets, the same functionality is obtained even in the absence of magnetic fields, paving the way for the creation of “thermoelectric permanent magnets” that exhibit efficient transverse thermoelectric conversion together with spontaneous magnetization. This study provides a new material design guideline for transverse thermoelectrics.

Pressure-induced remarkable four-phonon interaction and enhanced thermoelectric conversion efficiency in CuInTe2

Hydrostatic pressure (P) has been regarded as an effective approach to improve the performance of thermoelectric materials. Although a positive correlation between its thermoelectric performance and pressure has been demonstrated experimentally for CuInTe2, the underlying physical mechanism remains unclear. Herewith, we investigate the inherent mechanism of hydrostatic pressure-induced electron-thermal transport properties and thermoelectric conversion efficiency for CuInTe2. It is demonstrated that the pressure limits the thermal transport behavior of heat-carrying phonons by changing phonon dispersion, where the broadening of the low-lying phonon bandwidth caused by the compression promotes the dominance of the four-phonon (4ph) scattering mechanism, especially at high temperatures. In addition, the power factor has achieved a huge net increase through the convergence of the valence band edge despite the presence of strong coupling between electron transport parameters. Such bidirectional optimization gives rise to a remarkable enhancement of thermoelectric conversion efficiency. Our work highlights the significant effect of pressure-induced 4ph interaction in CuInTe2, which brings deeper insights into the behavior of thermoelectric materials under extreme pressure environments.

Wide-temperature-range thermoelectric n-type Mg3(Sb,Bi)2 with high average and peak zT values

Mg3(Sb,Bi)2 is a promising thermoelectric material suited for electronic cooling, but there is still room to optimize its low-temperature performance. This work realizes >200% enhancement in room-temperature zT by incorporating metallic inclusions (Nb or Ta) into the Mg3(Sb,Bi)2-based matrix. The electrical conductivity is boosted in the range of 300–450 K, whereas the corresponding Seebeck coefficients remain unchanged, leading to an exceptionally high room-temperature power factor >30 μW cm−1 K−2; such an unusual effect originates mainly from the modified interfacial barriers. The reduced interfacial barriers are conducive to carrier transport at low and high temperatures. Furthermore, benefiting from the reduced lattice thermal conductivity, a record-high average zT > 1.5 and a maximum zT of 2.04 at 798 K are achieved, resulting in a high thermoelectric conversion efficiency of 15%. This work demonstrates an efficient nanocomposite strategy to enhance the wide-temperature-range thermoelectric performance of n-type Mg3(Sb,Bi)2, broadening their potential for practical applications.

Machine learning based models to investigate the thermoelectric performance of carbon nanotube-polyaniline nanocomposites

Thermoelectric materials have been widely recognized as a simple approach for harnessing green energy by converting thermal gradients into electrical energy. However, the intricate and conflicting interplay between electrical conductivity (σ), Seebeck coefficient (S), and thermal conductivity (k) in known materials present a challenge for improving their thermoelectric conversion efficiency. To overcome this challenge, various data-driven machine-learning techniques such as correlation matrix (CM), multiple linear regression (MLR), polynomial regression (PR), principal component analysis (PCA), and artificial neural network (ANN) have been utilized to identify the impact of different structural and compositional factors on the thermoelectric performance in carbon nanotube (CNT)-polyaniline (PANI) based nanocomposites. Our findings suggest that the thermoelectric figure of merit, (ZT=S2σκT) of these nanocomposites can be positively influenced by proper choice of doping agent of PANI and by using SWCNT, since these two parameters influence the thermoelectric outputs in the desired manner. The other input variables have conflicting impacts on the thermoelectric performance, although optimal solutions for maximized performance can be extracted. The investigation provides valuable insights about designing a PANI-CNT nanocomposite system with superior thermoelectric performance.

Simultaneously Enhanced Energy Harvesting and Storage Performance Achieved by 3D Mix‐Phase Mose2‐Nise/NF

AbstractAs an energy harvesting device, the newly emerged thermocell has attracted great interest. However, it requires an additional energy storage device to complete a functional recycling system. As the core part of energy harvesting and storage devices, the design of electrodes with both high thermoelectric and electrochemical conversion efficiencies is particularly important. Herein, a high‐performance thermocell and supercapacitor device are constructed by employing the same mix‐phase MoSe2‐NiSe/NF electrode for both energy harvesting and storage. The thermocell exhibits an enhanced Seebeck coefficient of −1.69 mV K−1 and a superior output of 0.58 mW m−2 K−2 for low‐grade heat harvesting. Meanwhile, the supercapacitor device shows a great energy density of 54 Wh kg−1 at a power density of 806 W kg−1 and excellent cycling stability with a 92.8% retention rate after 50 000 cycles. This work offers a universal approach for the rational design of synergistic electrode materials to simultaneously achieve high‐energy harvesting and storage devices and lays a foundation for the recycling system of thermoelectric harvesting, conversion, and storage.

Performance analysis and optimization of a TEG-based compression hydrogen storage waste heat recovery system

A considerable quantity of waste heat is produced while compressing hydrogen. The process can be optimized by converting heat energy into electricity by utilizing thermoelectric electricity generator (TEG). This paper presents a TEG-based compression hydrogen storage waste heat recovery system (TEG-CHWSR). The effects of compression ratio, mass flow rate and inlet temperature at the cold and hot side on the operation performance and energy recovery efficiency are studied by establishing a mathematical model. The results demonstrate that the hydrogen inlet temperature and mass flow rate significantly impact the maximum output power and corresponding conversion efficiency of TEG. The maximum hydrogen storage pressures corresponding to the four types of hydrogen storage tanks are different. The maximum output power range of TEG for four hydrogen storage tanks is 2.32–5.9 kW at the TEG length of 1 m. The maximum output power and optimal module length increase with the increased hydrogen mass flow rate, while the energy recovery efficiency firstly increases and then decreases, existing a maximum point. The inlet temperature and mass flow rate at cold side has little influent on the optimal length of the TEG module. However, it has impact on the output power and thermoelectric conversion efficiency of TEG.

Performance Assessment of Closed-Brayton-Cycle and Thermoelectric Generator Combined Power Generation System Coupled with Hydrocarbon-Fueled Scramjet

Closed-Brayton-cycle (CBC) is a potential scheme to provide high-power electricity for hypersonic vehicles, but finite cold source onboard limits its power level. A thermoelectric generator (TEG) combined with CBC is a feasible power enhancement approach by extending the available temperature range of cold source. In this study, a performance assessment of the CBC-TEG combined power generation system coupled with hydrocarbon-fueled scramjet is performed to exhibit its possible operation characteristics and performance limitations on hypersonic vehicles. Results indicate that, at a fixed flight Mach number, a larger fuel equivalence ratio (φ) leads to a higher total electric power and CBC power but a lower TEG power. There are three limitations on the fuel equivalence ratio, TEG temperature difference, and combustion heat dissipation adjustment for the operation of CBC-TEG. The total power of CBC-TEG can be adjusted by φ, but the adjustable range becomes smaller at higher Ma. The electric quantity at unit fuel mass increases with φ, mainly due to the higher thermoelectric conversion efficiency. Moreover, the maximum value of the electric quantity at unit fuel mass for CBC-TEG reaches 277.0 kJ/kg, which is about 33.4% higher than that of standalone CBC.

Temperature-dependent interatomic force constants and phonon coherent resonance contribution in quaternary non-centrosymmetric chalcogenides BaAg2SnSe4

Phonon heat transfer by thermoelectric modules undoubtedly plays a pivotal role for the future waste heat recovery and utilization. BaAg2SnSe4, a prototypical glasslike compound among quaternary non-centrosymmetric chalcogenides, demonstrates remarkable thermoelectric performance due to its exceptionally low lattice thermal conductivity (κL). Even with a comprehensive grasp of the underlying cause behind ultra-low κL and the subsequent heightened thermoelectric conversion efficiency, the temperature-dependent lattice dynamics and glass-like attributes governing κL continue to pose unresolved questions. In this study, we investigate the phonon thermal transport properties of quaternary BaAg2SnSe4 by incorporating the influence of phonon coherent resonance, thereby departing from the conventional Peierls's framework. Based on the temperature dependence of the interatomic force constants and coherences’ contribution to total lattice thermal conductivity (κL(C)), we intriguingly observe that the particle-like driven lattice thermal conductivity (κL(P)) and κL(C) have the quite significant and dominant role for describing ultralow phonon transport behaviors in the middle-high-temperature regions. Specially, enhanced phonon anharmonicity coupled with excited coherent phonons due to increasing temperature yields two close values, with 700 K values of 0.16 and 0.13 W/mK predicted for BaAg2SnSe4, respectively, accelerating its application in thermoelectric field. Furthermore, we also find that the off-diagonal terms of heat flux operators in κL exist distinction for different phonons, with zero contribution modes exhibiting temperature-independent phonon coherence effect. Temperature response of the force constants tensors and coherent resonance proposed in our work can be employed as a powerful tool, which would substantially be expected to inspire a broad revisiting phonon transport study in various device applications, including advanced thermal barrier coatings and superior thermoelectrics.

Exceptional n-type thermoelectric ionogels enabled by metal coordination and ion-selective association.

Ionic liquid-based ionogels emerge as promising candidates for efficient ionic thermoelectric conversion due to their quasi-solid state, giant thermopower, high flexibility, and good stability. P-type ionogels have shown impressive performance; however, the development of n-type ionogels lags behind. Here, an n-type ionogel consisting of polyethylene oxide (PEO), lithium salt, and ionic liquid is developed. Strong coordination of lithium ion with ether oxygen and the anion-rich clusters generated by ion-preferential association promote rapid transport of the anions and boost Eastman entropy change, resulting in a huge negative ionic Seebeck coefficient (-15 millivolts per kelvin) and a high electrical conductivity (1.86 millisiemens per centimeter) at 50% relative humidity. Moreover, dynamic and reversible interactions among the ternary mixtures endow the ionogel with fast autonomous self-healing capability and green recyclability. All PEO-based ionic thermoelectric modules are fabricated, which exhibits outstanding thermal responses (-80 millivolts per kelvin for three p-n pairs), demonstrating great potential for low-grade energy harvesting and ultrasensitive thermal sensing.

Improved thermoelectric properties of Sb-doped Ti0.5Zr0.5NiSn alloy with refined structure induced by rapid synthesis processes

Thanks to the great advantage of preparation methods, the thermoelectric (TE) alloy materials can be fast synthesized with controllable structural morphology for optimizing charge and phonon transport properties, thereby improving the TE efficiency of the material. Herein, a series of Sb-doped Ti0.5Zr0.5NiSn1−xSbx based half-Heusler alloy was prepared via a combined fast procedure of arc melting (AC), melt spinning (MS) followed by spark plasma sintering (SPS). The detailed analyses of morphology, phase structure, and composition reveal high-quality samples through processes for enhanced TE properties. High ZT values over one are achieved for all samples with slight Sb doping content variation from x = 0.0025–0.02. The enhanced TE performance of the Sb-doped Ti0.5Zr0.5NiSn1−xSbx alloys here results from the synergistic between the approaches such as doping, alloying, nanostructuring, and the presence of nano-precipitates induced by MS. The highest ZT values of ∼1.2 at 847 K with an average ZT of 0.798 and estimated TE conversion efficiency reached 12.8% in the temperature range from 300 K to 847 K were achieved for the 1.25% Sb doped sample. In addition, the thermal cycling test through continuous measurement of five and a half cycles confirmed the high thermal stability of the bulk alloy. High ZT and thermal stability based on Hf-free Ti0.5Zr0.5NiSn1−xSbx alloy and fast synthesis are well matched for commercial requirements.

Structural optimization of solar thermoelectric generators considering thermal stress conditions

The optimization of the thermoelectric leg (TEL) structure is an effective means which can improve the thermoelectric performance of solar thermoelectric generator (STEG), however, the optimized dimensions may not satisfy the allowed stress and thus prevent the STEG from normal operation properly. To address this issue, we constructed a coupled thermal-electrical-stress multi-physical field model of STEG, and optimized the STEG structure under the condition of allowed stress. The results show that when the allowed stress is not considered, the optimal ratio of cross-sectional ratio (f) to height (h) is 0.03 mm−1 to maximize the thermoelectric conversion efficiency, but then the maximum thermal stress of the STEG far exceeds the allowed stress of the material. When the allowed stress conditions are considered, the critical cross-sectional ratio of the module is much higher than the optimal cross-sectional ratio. The critical output power that can be obtained from the module is 38.5% less than the maximum output power without considering the allowed stress, and the influence of thermal stress on the optimal structural parameters is significant at a high concentration ratio. The critical output power gradually increases with the increase in the concentration ratio, and a greater output performance can be obtained at larger heights, while a greater output power density can be obtained at smaller heights. The outcomes presented by this study have certain guide to the construction of high-efficiency STEG.

Investigation of neutronic and thermal–electric coupling phenomenon in a 100 kWe-level nuclear silent heat pipe-cooled reactor

Heat pipe-cooled reactors are attractive because of their compact structure, high power capacity and reliability, and inherent safety features. These reactors are distinguished by the use of high-temperature heat pipes that directly bridge the reactor core and energy conversion devices, thus creating a tightly knit modular system. However, comprehensive coupled analysis of these reactors remains challenging because of the intricate multiphysics interactions involved. To address this, the neutronic and thermoelectric coupled phenomena of heat pipe-cooled reactors are investigated in this study. Models are introduced for the point reactor kinetics, core heat transfer, channel heat transfer, two-phase two-dimensional heat pipes, thermoelectric coupling, and cold plates. The channel heat transfer is refined in a 100 kWe-level nuclear silent heat pipe-cooled reactor and a model for the three-dimensional heat transfer process in its thermoelectric matrix established, which effectively resolves the calculation distortions of the lumped model. The maximum deviation between the calculation results from the proposed model and the verification data for a full-system coupled computation is less than 10 K. The core temperature difference from the three-dimensional model is five times that of the lumped model with a maximum average fuel temperature difference of 225.7 K. The maximum and average thermoelectric conversion efficiencies are 15.56 % and 14.43 %, respectively. The failures of one, five, and nine heat pipes are analysed. The failure of a single heat pipe has negligible effects with a peak fuel temperature surge of only 121 K. In contrast, a failure involving nine heat pipes leads to a peak fuel temperature spike of 778 K and a 47.1 % increase in the maximum heat transfer power, marking a critical operational threshold. It is therefore imperative to consider the safety margin in the potential failure of multiple central heat pipes during the preliminary design stages.

Magnetoelectric coupling and thermoelectric behaviors in Ni-doped CuCrO[formula omitted] crystallites

A novel and effective approach to improve thermoelectric conversion efficiency is of utmost importance for its commercial viability. The increased ferromagnetism caused by the Ni-doping alters the antiferromagnetic interactions between Cr3+ ions in CuCrO2 and likely produces the conical-like spin component. The magnetostrictive ferromagnetic Ni2+ doped CuCrO2 generates stress through the elastic property at the grain interface and piezoelectricity which couples and generates an electric field. The built-in electric field and magnetic scattering produced by magnetic doping reduce carrier concentration and mobility and raise the Seebeck coefficient. The engendered multiferroic nature and the alteration of electron transport properties with magnetic phase transition from ferromagnetic to paramagnetic of Ni2+ doped CuCrO2 are evidenced by magnetoresistance and vibrating-sample magnetometry (VSM) investigations. The magnetic inclusion of Ni2+ generates carrier magnon drag which steers the highest Seebeck coefficient of 625 μV/K at 100 °C. The conductivity of 4203 S/m and the Seebeck coefficient of 386 μV/K leads excellent power factor (S2σ) of 0.62 mW/mK2 and ZT of 0.163 at 700 °C. The Ni2+ dopants, on the other hand, cause broad frequency phonon scattering, which significantly lowers the lattice thermal conductivity of CuCrO2. This study demonstrates how magnetic particle-induced thermoelectromagnetic coupling effects can significantly boost the efficiency of electro-thermal conversion.

Effects of vacancy defects on vibrational properties of Ni–Al

The phonon spectra of Ni, Al, and NiAl, as well as their electronic characteristics, are investigated using density functional theory and density functional perturbation theory. Our research on phonon dispersion has concentrated on every high symmetry point of NiAl, both with and without defects. The phonon gap of NiAl is measured to be 1.78 THz between the lowest value of the optical branch and the top bound of the acoustic branch. The NiAl supercell with a center Al vacancy was built to investigate the effects of defects on its vibrational characteristics. The phonon gap of a NiAl crystal at the center of the Brillouin zone with no defect is calculated to be 1.06 THz. This value of the phonon gap is affected by the Al vacancy defect and decreases by 7.67%. The development of phonon spectrum is investigated using electronic structure and properties. The majority of free electrons accumulated at the Fermi level contribute to promoting the vibration. The importance of a heavier element in a compound has also been explored in terms of gap tuning. Reduced thermal conductivity by narrowing the gap between optical and acoustic modes raises the figure of merit (zT) value, which improves the thermoelectric energy conversion efficiency.