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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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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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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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Effect of substrate temperature on structural and thermoelectric properties of RF-magnetron sputtered SnSe thin film
摘要： SnSe is a potential thermoelectric material, but there are few reports about the thermoelectric properties of the film. In this work, SnSe thin films were deposited on glass substrates by RF magnetron sputtering from SnSe alloy target. The effect of substrate temperature on the structural and thermoelectric properties was investigated. It was found that the columnar grains and the surface roughness of the films increase with increasing the substrate temperature. The film deposited at 558 K exhibited a high crystalline quality and stoichiometric composition, which has a maximum power factor of 1.4 uWcm-1K-2 at 575 K. The results of this work demonstrate the importance of high substrate temperature to obtain high thermoelectric performance SnSe films.
关键词： SnSe thin film,sputtering,thermoelectric properties
更新于2025-09-23 15:22:29
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Influence of Local Heterojunction on the Thermoelectric Properties of Mo-SnSe Multilayer Films Deposited by Magnetron Sputtering
摘要： Mo-SnSe multilayer films were deposited by multi-step magnetron sputtering. The Mo-SnSe multilayer films are then annealed, and the new phases including SnSe2 and MoSe2 are observed by x-ray diffraction and Raman spectroscopy. Scanning electron microscopy reveals that the SnSe exhibits the columnar grain structure with sizes from 50–100 nm. The high-resolution transmission electron microscopy shows the SnSe2 is dispersed at the boundary of the columnar grain and the local MoSe2/SnSe heterojunction is formed in the interior of the columnar grain. The influence of Mo content on the thermoelectric properties of SnSe thin films was investigated. A maximum power factor of 0.44 μW cm?1 K?2 was obtained for a 2.6 at.% Mo-doped SnSe thin film at 576 K, which is higher than that of a SnSe thin film deposited under the same conditions.
关键词： thermoelectric properties,heterojunction,SnSe films,sputtering
更新于2025-09-23 15:22:29
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Electronic and Vibrational Properties of TiS <sub/>2</sub> , ZrS <sub/>2</sub> , and HfS <sub/>2</sub> : Periodic Trends Studied by Dispersion-Corrected Hybrid Density Functional Methods
摘要： The electronic and vibrational properties of TiS2, ZrS2, and HfS2 have been studied using dispersion corrected hybrid density functional methods. The periodic trends in electronic band structures, electronic transport coefficients, IR and Raman spectra, and phonon dispersion relations were investigated. Comparison to the available experimental data shows that the applied DFT methodology is suitable for the investigation of the layered transition metal dichalcogenide materials with weak interlayer Van der Waals interactions. The choice of damping function in the D3 dispersion correction proved to have surprisingly large effect. Systematic investigation of the periodic trends within group 4 disulfides reveals that TiS2 shows many differences to ZrS2 and HfS2 due to the more covalent M–S bonding in TiS2. ZrS2 and HfS2 mainly show differences for properties where the atomic mass plays a role. All three compounds show similar Seebeck coefficients, but clear differences in the relative electrical conductivity of cross- and in-plane directions. The transport and vibrational properties of thin TiS2 single crystals were also investigated experimentally.
关键词： ZrS2,HfS2,dispersion corrected hybrid density functional methods,thermoelectric properties,periodic trends,vibrational properties,electronic properties,TiS2
更新于2025-09-23 15:21:01
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Effect of DFT methods on electronic structure and <i>K</i> -absorption spectra of InPS <sub/>4</sub> : detailed studies of the optical, thermoelectric and elastic properties
摘要： The effect of exchange-correlation potential on InPS4 electronic structure was studied by applying GGA, GGA+U, mBJ, and mBJ+U potentials in the Kohn–Sham framework. The use of mBJ+U in full potential APW+lo method results in reliable K-absorption spectrum, which consists of nearly full experimental peaks of right intensity. The remarkable discrepancy between 1e w^( ) and 1e w?( ) occurs at 0 eV, 4 eV, 6 eV, and 9.5 eV, indicating the strong anisotropic optical properties of InPS4 at these energy levels. At 4 eV, the optical absorption of InPS4 has high order of 105cm?1 magnitude for wide energy range, at least within 4–20 eV. The figure of merit ZT achieves its highest value of about 0.8–1. InPS4 is a p-type semiconductor for chemical potential μ ranging from 0 eV to about 1.6 eV, but it is an n-type semiconductor for μ of about 1.6–2.7 eV. The Poisson’s ratio is equal to 0.26 and B/G@1.75. Indium thiophosphate InPS4 possesses rather low deformation resistance with the Young and shear moduli of 38.47 GPa and 15.27 GPa, respectively.
关键词： thermoelectric properties,elastic properties,optical properties,ab initio calculations,x-ray spectrum
更新于2025-09-23 15:19:57
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Heat and charge transport in bulk semiconductors with interstitial defects
摘要： Interstitial defects are inevitably present in doped semiconductors that enable modern-day electronic, optoelectronic, or thermoelectric technologies. Understanding the stability of interstitials and their bonding mechanisms in the silicon lattice was accomplished only recently with the advent of first-principles modeling techniques, supported by powerful experimental methods. However, much less attention has been paid to the effect of different naturally occurring interstitials on the thermal and electrical properties of silicon. In this work, we present a systematic study of the variability of heat and charge transport properties of bulk silicon, in the presence of randomly distributed interstitial defects (Si, Ge, C, and Li). We find through atomistic lattice dynamics and molecular dynamics studies that interstitial defects scatter heat-carrying phonons to suppress thermal transport—1.56% of randomly distributed Ge and Li interstitials reduce the thermal conductivity of silicon by ～30 and 34 times, respectively. Using first-principles density functional theory and semiclassical Boltzmann transport theory, we compute electronic transport coefficients of bulk Si with 1.56% neutral Ge, C, Si, and Li interstitials, in energetically favorable hexagonal, tetrahedral, split-interstitial, and bond-centered sites. We demonstrate that hexagonal-Si and hexagonal-Ge interstitials minimally impact charge transport. As an illustration of the relevance of this work for practical applications, we predict the thermoelectric property of an experimentally realizable bulk Si sample that contains Ge interstitials in different symmetry sites. Our research establishes a direct relationship between the variability of structures dictated by fabrication processes and heat and charge transport properties of silicon. The relationship provides guidance to accurately estimate performance of Si-based materials for various technological applications.
关键词： electronic transport,thermoelectric properties,interstitial defects,silicon,thermal conductivity
更新于2025-09-19 17:15:36
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Enhanced thermoelectric properties of InSb: Studies on In/Ga doped GaSb/InSb crystals
摘要： In/Ga elements were doped in GaSb/InSb crystals respectively, and their thermoelectric performances were studied. The crystals had cubic zinc blende structure with change in lattice parameters. The charge transfer occurred between all the three (In, Ga and Sb) elements when In was doped with GaSb. Whereas in Ga doped InSb crystals, the charge transfer occurred only among Ga and Sb elements. In/Ga doped GaSb/InSb crystals exhibited degenerate and non-degenerate electrical properties, respectively. Optical modes of phonon vibrations were present, and their transverse mode was dominant over longitudinal mode in all the samples. The thermoelectric ?gure of merit (ZT) of In doped GaSb crystals were low because of their low power factor and high thermal conductivity. The highest power factor (59.5 μW/cmK2) and ZT (0.56) at 573 K were achieved by Ga doped (1 × 1021/cm3) InSb crystal. The ZT 0.56 at 573 K is thus far the highest among other reported values of InSb crystals.
关键词： D. Point defect,B. Thermoelectric properties,A. Intermetallics,C. Crystal growth,G. Thermoelectric power generation
更新于2025-09-10 09:29:36
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Microstructure and thermoelectric properties of In2O3/ITO thin film thermocouples with Al2O3 protecting layer
摘要： In2O3/ITO thin film thermocouples (TFTCs) with alumina protecting layer were fabricated on alumina substrates. The effects of protecting layer on their performance at higher temperature and long term service were investigated accordingly. In2O3 and ITO thin films were prepared by radio frequency magnetron sputtering methods, while the alumina protecting layer was prepared by traditional spin-coating methods. Microstructural and thermoelectric properties of the In2O3/ITO TFTCs with and without alumina (Al2O3) protecting layer were investigated as a function of sintering time from 2 to 10 h at 1250 °C. The results show that, the existence of alumina protecting layer can effectively increase the performance capabilities of thermocouples at high temperatures by inhibiting the volatilization of the thin film. In2O3/ITO TFTCs with protecting layer can work normally over 10 h at 1250 °C while Seebeck coefficient is 131.7 μV/°C. The drift rate can reach 3.05 °C/h, which is much better than those without protecting layer.
关键词： high temperature,thermoelectric properties,Al2O3 protecting layer,long term service,In2O3/ITO thin film thermocouples
更新于2025-09-10 09:29:36