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Grain growth mechanism and thermoelectric properties of hot press and spark plasma sintered Na-doped PbTe
摘要： We investigated he thermoelectric (TE) properties and microstructures of Na-doped PbTe compounds, synthesized by various milling and sintering processes. It has been generally accepted that spark plasma sintering (SPS) inhibits grain growth due to the short sintering time, which is bene?cial to the nano bulk composite. In contrast, we observed abnormal grain growth for SPS, unlike hot press (HP) sintering. Considering the Gibbs free energy change during sintering, the HP sintering increases internal energy while the SPS increases entropy energy, which causes the abnormal grain growth. Lattice strain and Fourier transform analyses of the transmission electron microscope images showed that the SPS sintered samples had more signi?cant lattice strains and defects than the HP sintered samples. The low thermal conductivity of the SPS sintered samples was not from grain boundary phonon scattering but from phonon scattering by lattice strains and defects. The lattice strains and defects decreased electrical conductivity as well, resulting in deterioration of the power factor and thermoelectric performance. This suggests that the lattice strains and defects are more critical factors for enhancing thermoelectric per- formance than particle and grain size control.
关键词： Grain growth,Thermoelectric,Hot press,Spark plasma sintering,ZT
更新于2025-11-21 10:59:37
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Cu/Sb Codoping for Tuning Carrier Concentration and Thermoelectric Performance of GeTe-Based Alloys with Ultralow Lattice Thermal Conductivity
摘要： Pristine GeTe shows promising thermoelectric performance but is limited by the high carrier concentration (nH) from Ge vacancies and thermal conductivity. Herein, Cu/Sb was chosen as codopants to suppress the high nH and to decrease thermal conductivity. In this condition, a promising zT of ～1.62 under 773 K was acquired in the Ge0.85Te(CuSb)0.075 system proposed in this paper/work. Results show that as the dopant concentration increases, the power factor rises due to the reduction of the nH to ～1 × 1020 cm?3. Apart from this, the total thermal conductivity also declines from ～7.4 W m?1 K?1 to ～1.59 W m?1 K?1 originating from an ultralow lattice thermal conductivity, in which the multiscatter mechanism from grain boundaries and point defect disperses the frequency phonons di?erently. The ?ndings in this paper combine thermal and electronic strategies and lay the foundation to develop Pb-free thermoelectric materials.
关键词： multiscatter mechanism,Cu/Sb codoped GeTe,thermoelectric materials,ultralow lattice thermal conductivity,zT value,carrier concentration,Seebeck coefficient
更新于2025-11-14 17:03:37
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Free-standing highly conducting PEDOT films for flexible thermoelectric generator
摘要： Recently, organic thermoelectric (TE) materials especially conducting polymers have attracted increasing attention. In this work, we successfully synthesized ultrafine poly (3,4-ethylenedioxythiophene) (PEDOT) nanowires (NWs) (~10 nm) by a simple self-assembled micellar soft-template method and then obtain highly flexible free-standing PEDOT NW films by vacuum-assisted filtration. The films are with very high electrical conductivity (~1340 S cm?1). After being treated with 6 M H?SO? and then with 1 M NaOH at room temperature, the film shows an enhanced power factor of 46.51 μW m?1 K?2 (Seebeck coefficient of 25.5 μV K?1, electrical conductivity of 715.3 S cm?1), which increases by 54% compared with that of the pristine film. To the best of our knowledge, it outperforms the TE performance of all reported one-dimensional conducting polymer-based films. In addition, the TE performance of the film almost remains unchanged even after being bent for 200 times, indicating excellent flexibility. A flexible TE prototype composed of six strips (7 mm × 30 mm) of the as-prepared PEDOT NW films connected in series shows an output power of 157.2 nW at a temperature difference of 51.6 K. The free-standing PEDOT NW films show promise to a new generation of wearable TE devices.
关键词： Flexible,Thermoelectric,Free-standing,PEDOT,Highly conductive
更新于2025-09-23 15:23:52
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First principles study of electronic structures of Cd0.9375Co0.0625X (X?=?S, Se, Te) for magnetic, optical and thermoelectric device applications
摘要： The present article investigates the structural and electronic properties of Co doped (xCo = 6.25%) CdS/Se/Te diluted magnetic semiconductors to understand the optical and thermoelectric characteristics. The electronic properties, computed by applying generalized gradient approximation (GGA) and then modified Becke Johnson (mBJ) functional, are contrasted to identify the appropriate electronic parameters. The stable ferromagnetic states have been justified to arise due to the p-d hybridization that has been found responsible in inducing magnetic moments at the interstitial and at the non-magnetic sites. The computed direct band gap and the exchange constants (N0α and N0β) have suggested, respectively, the potential optical and spintronic device applications. The studied compounds operate within visible-ultraviolet energy range. The thermoelectric response improves with temperature, while deteriorated due to Co doping. The studied compounds exhibiting various significant physical properties evidence the potential consumption in various technologically important spintronic, optoelectronic and thermoelectric devices.
关键词： Optical properties,Ferromagnetism,Diluted magnetic semiconductors,Thermoelectric properties,mBJ potential
更新于2025-09-23 15:23:52
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Elastic, electronic and thermoelectric properties of Sr3MN (M?= Sb, Bi) under pressure
摘要： We have performed first-principles calculations to study the structural, elastic, electronic and thermoelectric properties of Sr3MN (M = Sb, Bi) under pressure. The optimized lattice parameters are in good agreement with the available experimental and theoretical measurements. Brittle to ductile transition occurs at 15 GPa and the hardness of both compounds decreases with the increase of pressure. The band gap slightly reduces with pressure and both compounds exhibit semiconducting nature for TB-mBJ potential. The density of states increases slightly at the Fermi level. The inclusion of the spin-orbit coupling effect reduces the band gap of Sr3BiN. The calculated Seebeck coefficient for Sr3SbN and Sr3BiN at 15 GPa and 600 K are 257 and 142 μV/K, respectively. The calculated lattice thermal conductivity of both compounds decreases with the increase of pressure, as phonon scattering increased. The predicted thermoelectric figure of merit (ZT) for Sr3SbN and Sr3BiN at 15 GPa and 600 K are 0.71 and 0.63, respectively. The obtained thermoelectric properties at high pressure making them suitable for thermoelectric device applications.
关键词： Lattice thermal conductivity,Pressure effect,Thermoelectric properties,Electronic properties,Elastic properties
更新于2025-09-23 15:23:52
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Investigation of Structural and Elastic Stability, Electronic, Magnetic, Thermoelectric, Lattice-Dynamical and Thermodynamical Properties of Spin Gapless Semiconducting Heusler Alloy Zr2MnIn Using DFT Approach
摘要： In recent times, spin gapless semiconductors (SGS) have attracted much attention as a promising candidate for spintronics and thermoelectric applications due to their high carrier concentration and good thermoelectric figure of merit. In this paper, we have carried out a systematic theoretical investigation of the structural, elastic, thermal, electronic, magnetic, thermoelectric, lattice dynamical and thermodynamical properties of Zr2MnIn using density functional theory (DFT) based first principle calculations. The band structure calculation shows indirect band gap in a spin down channel and zero band gap in a spin up channel of valence and conduction bands confirming the spin gapless semiconducting nature of Zr2MnIn. The structural and dynamical stability of the antiferromagnetic phase of Zr2MnIn has also been investigated. Magnetization in Zr2MnIn originates due to the d state electrons of Zr atoms, which follows the Slater Pauling rule: Mt = Zt (cid:2) 18. Phonon dispersion curves exhibit real frequency of phonon modes throughout the Brillouin zone, which confirms the dynamical stability of the antiferromagnetic phase of Zr2MnIn. Thermodynamical properties including specific heat and Debye temperature have been calculated using phonon density of states. A higher value of the thermoelectric figure of merit 1.25, predicts that this alloy as good thermoelectric properties with better output efficiency.
关键词： Spin gapless semiconductor (SGS),magnetic moment,structural and elastic stability,thermoelectric and lattice dynamical properties,electronic structure
更新于2025-09-23 15:23:52
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[IEEE 2018 Conference on Electrotechnology: Processes, Models, Control and Computer Science (EPMCCS) - Kielce, Poland (2018.11.12-2018.11.14)] 2018 Conference on Electrotechnology: Processes, Models, Control and Computer Science (EPMCCS) - Investigation and Determination of Efficiency of the Waste Heat Recovery System Using Peltier Modules
摘要： High efficiency technology of waste heat energy utilization would change the face of the energy market. Due to the fact that the energy system and transport are based on fossil fuels, there is a huge potential for its efficient use. Despite the fact that the technology of Peltier semiconductor modules has been known for many years, there are no solutions that might be commonly disseminated. There is also a deficit of available sources that in a transparent, coherent and synthetic way could provide guidelines for the constructors of such devices, and show how much energy they can generate and what efficiency they have. Moreover, the Peltier modules available on the market are burdened with many stereotypes. When trying to use this technology, it should be remembered that in addition to the Peltier phenomenon, the module's operation is based on four other physical phenomena: two of them have a negative impact and they determine the practically obtained parameters of the Peltier module. These are: Joule effect and heat conduction phenomenon. The other two phenomena: Seebeck and Thomson ones, play slightly smaller roles. The aim of the authors was to investigate the self-made model of a thermoelectric generator TEG, constructed using Peltier modules. The paper presents the results of measurements and the method of determining the electrical efficiency of this model. Additionally, a temperature range was determined at that such recovery has a measurable utilitarian aspect and economic sense. The limitations of semiconductor technology of Peltier cells have been given, and design guidelines at construction process of such systems to optimize their efficiency are presented.
关键词： Seebeck effect,thermoelectric generator TEG,determination of efficiency,Peltier module
更新于2025-09-23 15:23:52
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Compositional analysis by RBS, XPS and EDX of ZnO:Al,Bi and ZnO:Ga,Bi thin films deposited by d.c. magnetron sputtering
摘要： Rutherford backscattering spectrometry, X-ray photoelectron and X-ray energy dispersive spectroscopies were employed to analyse Bi incorporation into ZnO:Al and ZnO:Ga transparent and electrically conductive thin films deposited by d.c. magnetron sputtering, with thickness in the range of 300–400 nm. Sputtering was performed in an argon atmosphere from two targets in confocal geometry being one composed of either ZnO:Al2O3 or ZnO:Ga2O3 composites and the other a Bi metal target. The content of bismuth dopant in the ZnO matrix was controlled by the respective target current density (JBi) in order to attain a high optical transparency (> 80%) in the visible region. For ZnO:Al,Bi films Bi content varied from 0.1 to a maximum of 1.5 at.% when varying JBi from 0.06 to 0.26 mA cm?2. However, for ZnO:Ga,Bi films, deposited in similar conditions, Bi reached a maximum overall layer content of 2.4 at.%, with a surface enrichment content that varied from 1.3 to 8.8 at.%. It was also observed that the Bi content in the topmost layers of the films is slightly depleted due to thermal evaporation upon thermal annealing in vacuum at 350 °C. It is envisaged applications for these films as transparent photoelectrodes and thermoelectric materials.
关键词： Ga,Bismuth,TCO,Doping,Thermoelectric,Al,XPS,RBS,PIXE,ZnO
更新于2025-09-23 15:23:52
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Roles of Carrier Doping, Band Gap, and Electron Relaxation Time in the Boltzmann Transport Calculations of a Semiconductor’s Thermoelectric Properties
摘要： Although there is a growing demand for first-principles predictions of the thermoelectric properties of materials, the contribution of various errors in Boltzmann transport calculations is not negligible. We conducted a typical first-principles calculation and a Boltzmann transport analysis on a typical semiconductor (Si) at various temperatures T while varying the band gap ?g, electron relaxation time ?el, and phonon thermal conductivity ?ph to demonstrate how the calculated thermoelectric properties, which are functions of the carrier doping level, are affected by these parameters. Bipolar conduction drastically decreased zT via a degradation of the Seebeck coefficient S and an increase in the effective Lorenz factor Leff, indicating the importance of a wide enough ?g (several multiples of kBT or higher) for high zT. Thus, the underestimation of ?g, which frequently happens in first-principles calculations, could induce large errors in calculations for narrow-gap semiconductors. The calculation of the electron thermal conductivity without Peltier thermal conductivity was found to limit the zT of typical semiconductors to below 1. A small value of ?ph/?el, where ?ph/?el is the degree to which a material is a phonon-glass electron-crystal, was necessary to achieve a high zT. Fitting the calculations with experimental thermoelectric properties showed that ?el can vary by an order of magnitude from 10115 to 10114 s, depending on both T and the samples. This indicates that the use of a fixed relaxation time is inappropriate for thermoelectric materials.
关键词： Boltzmann transport calculation,first-principles calculation,thermoelectric properties
更新于2025-09-23 15:23:52
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Sharp increase in the density of states in PbTe upon approaching a saddle point in the band structure
摘要： PbTe is a leading mid-range thermoelectric material with a zT that has been enhanced by, amongst other methods, band engineering. Here we present an experimental study of the Hall effect, quantum oscillations, specific heat, and electron microprobe analysis that explores the evolution of the electronic structure of PbTe heavily doped with the 'ideal' acceptor Na up to the solubility limit. We identify two phenomenological changes that onset as the electronic structure deviates from a Kane-type dispersion at around 180 meV; a qualitative change in the field dependence of the Hall effect indicative of an increase in the high-field limit and a change in the Fermiology, and a sharp increase in the density of states as a function of energy. Following consideration of three possible origins for the observed phenomenology we conclude that the most likely source is nonellipsoidicity of the L pocket upon approach to a saddle point in the band structure, which is evidenced directly by our quantum oscillation measurements. Comparison to density functional theory calculations imply that this evolution of the electronic structure may be a key contributor to the large thermopower in PbTe.
关键词： band structure,PbTe,Hall effect,density of states,thermoelectric,quantum oscillations
更新于2025-09-23 15:23:52