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- 实验方案
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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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-type PbTe from first principles
摘要： We present an ab initio study that identifies the main electron-phonon scattering channels in n-type PbTe. We develop an electronic transport model based on the Boltzmann transport equation within the transport relaxation time approximation, fully parametrized from first-principles calculations that accurately describe the dispersion of the electronic bands near the band gap. Our computed electronic mobility as a function of temperature and carrier concentration is in good agreement with experiments. We show that longitudinal optical phonon scattering dominates electronic transport in n-type PbTe, while acoustic phonon scattering is relatively weak. We find that scattering due to soft transverse optical phonons is by far the weakest scattering mechanism, due to the symmetry-forbidden scattering between the conduction band minima and the zone center soft modes. Soft phonons thus play the key role in the high thermoelectric figure of merit of n-type PbTe: they do not degrade its electronic transport properties although they strongly suppress the lattice thermal conductivity. Our results suggest that materials like PbTe with soft modes that are weakly coupled with the electronic states relevant for transport may be promising candidates for efficient thermoelectric materials.
关键词： electron-phonon scattering,transport relaxation time approximation,thermoelectric materials,Boltzmann transport equation,n-type PbTe
更新于2025-09-23 15:21:01
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Thermal stability study of transition metal perovskite sulfides
摘要： Transition metal perovskite chalcogenides, a class of materials with rich tunability in functionalities, are gaining increased attention as candidate materials for renewable energy applications. Perovskite oxides are considered excellent n-type thermoelectric materials. Compared to oxide counterparts, we expect the chalcogenides to possess more favorable thermoelectric properties such as lower lattice thermal conductivity and smaller band gap, making them promising material candidates for high temperature thermoelectrics. Thus, it is necessary to study the thermal properties of these materials in detail, especially thermal stability, to evaluate their potential. In this work, we report the synthesis and thermal stability study of five compounds, a-SrZrS3, b-SrZrS3, BaZrS3, Ba2ZrS4, and Ba3Zr2S7. These materials cover several structural types including distorted perovskite, needle-like, and Ruddlesden–Popper phases. Differential scanning calorimeter and thermogravimetric analysis measurements were performed up to 1200 °C in air. Structural and chemical characterizations such as X-ray diffraction, Raman spectroscopy, and energy dispersive analytical X-ray spectroscopy were performed on all the samples before and after the heat treatment to understand the oxidation process. Our studies show that perovskite chalcogenides possess excellent thermal stability in air at least up to 550 °C.
关键词： differential scanning calorimeter,thermoelectric materials,Transition metal perovskite chalcogenides,thermal stability,thermogravimetric analysis,Raman spectroscopy,Ruddlesden–Popper phases,X-ray diffraction,energy dispersive analytical X-ray spectroscopy
更新于2025-09-23 15:21:01
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Probing of Thermal Transport in 50-nm Thick PbTe Nanocrystal Film by Time-Domain Thermoreflectance
摘要： Bottom-up fabrication of thermoelectric (TE) materials from colloidal nanocrystal (NC) building blocks can substantially increase their TE efficiency, e.g., by reducing lattice thermal conductivity. In this work, 10-nm spherical phase-pure oleate-capped PbTe NCs with narrow size distribution were synthesized and employed to fabricate 50-nm thick films on insulating SiO2/Si substrates. The spin-coating, with subsequent ligand exchange procedure, was applied to enhance coupling interactions between the NCs. Using dark conductivity measurements, we confirmed the semiconducting behavior and the Schottky-type electrical field-dependent conductivity mechanism in the resultant thin films. The thermal transport in the thin-film was probed by means of a time-domain thermoreflectance (TDTR) method. For this purpose, we used a customized state-of-the-art system based on a picosecond thermoreflectance instrument, which enables area-selective analysis with spatial resolution down to 5 μm. The results show that as-fabricated PbTe NC films exhibit ultralow thermal conductivity of 0.9 W m–1 K–1 at 300 K. The transport property findings suggest potential in the proposed quick and cost-effective spin-coating strategy for bottom-up fabrication of nanostructured TE films from high-quality colloidal NC building blocks.
关键词： colloidal nanocrystals,spin-coating,thermoelectric materials,thermal conductivity,time-domain thermoreflectance,PbTe
更新于2025-09-23 15:21:01
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Effect of Oxygen Partial Pressure on the Phase Stability of Copper–Iron Delafossites at Elevated Temperatures
摘要： Oxide-based materials are promising candidates for use in high temperature thermoelectric generators. While their thermoelectric performance is inferior to commonly used thermoelectrics, oxides are environmentally friendly and cost-effective. In this study, Cu-based delafossites (CuFeO2), a material class with promising thermoelectric properties at high temperatures, were investigated. This work focuses on the phase stability of CuFeO2 with respect to the temperature and the oxygen partial pressure. For this reason, classical material characterization methods, such as scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction, were combined in order to elucidate the phase composition of delafossites at 900 ?C at various oxygen partial pressures. The experimentally obtained results are supported by the theoretical calculation of the Ellingham diagram of the copper–oxygen system. In addition, hot-stage X-ray diffraction and long-term annealing tests of CuFeO2 were performed in order to obtain a holistic review of the phase stability of delafossites at high temperatures and varying oxygen partial pressure. The results support the thermoelectric measurements in previous publications and provide a process window for the use of CuFeO2 in thermoelectric generators.
关键词： high temperature thermoelectric materials,delafossite,thermoelectric generator (TEG),phase stability,Ellingham diagram
更新于2025-09-19 17:15:36
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Thermoelectric Properties of (100) Oriented Silicon and Nickel Silicide Nanocomposite Films Grown on Si on Insulator and Si on Quartz Glass Substrates
摘要： We have grown (100) oriented composite films of Si and Ni silicide nanocrystals (Ni–Si NC film) on substrates of Si on insulator (SOI) and Si on quartz glass (SOQ). Owing to improvement of carrier transport properties and reduction of the thermal conductivity in the oriented films, they have higher dimensionless figures of merit, ZT of 0.22–0.42 for p-type Ni–Si NC film and 0.08–0.13 for n-type Ni–Si NC film than that of bulk Si (ZT < 0.01) at 30°C. The ZT values of p-type and n-type Ni–Si NC films were increased to 0.65 and 0.40 at 500°C, respectively.
关键词： silicon based thermoelectric materials,nanocomposite films,nickel silicide nanocrystals,silicon nanostructures,phonon scattering
更新于2025-09-19 17:15:36
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Doping of Donor-Acceptor Polymers with Long Side Chains via Solution Mixing for Advancing Thermoelectric Properties
摘要： One-step doping of conjugated polymers by solution mixing is typically performed instead of sequential doping because of its simplicity. However, doped polymer solutions often exhibit poor solubility, and the presence of dopants in the produced films can disturb the molecular ordering of polymer structures. In this work, effective pairs of two donor-acceptor (D-A) type polymers and a molecular dopant characterized by high solution stability and good thermoelectric properties of the prepared thin films have been reported. The presence of long side chains in the polymer structures preserves their original solubilities and crystallinity in the solution and thin-film states, respectively, even at large amounts of added dopant (up to 38 mol%). Furthermore, the relatively shallow levels of the highest occupied molecular orbitals of the selected D-A polymers enable efficient charge transfer from the dopant species. Owing to their good charge transport properties, the doped D-A polymers exhibit outstanding thermoelectric properties with a maximum power factor of 31.5 μW m?1 K?2, which is more than an order of magnitude higher than those of the control samples prepared from donor-only poly(3-hexylthiophene).
关键词： molecular doping,donor-acceptor polymers,power factors,long side chains,solution mixing,organic thermoelectric materials
更新于2025-09-19 17:15:36
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Polymer morphology and interfacial charge transfer dominate over energy-dependent scattering in organic-inorganic thermoelectrics
摘要： Hybrid (organic-inorganic) materials have emerged as a promising class of thermoelectric materials, achieving power factors (S2σ) exceeding those of either constituent. The mechanism of this enhancement is still under debate, and pinpointing the underlying physics has proven dif?cult. In this work, we combine transport measurements with theoretical simulations and ?rst principles calculations on a prototypical PEDOT:PSS-Te(Cux) nanowire hybrid material system to understand the effect of templating and charge redistribution on the thermoelectric performance. Further, we apply the recently developed Kang-Snyder charge transport model to show that scattering of holes in the hybrid system, de?ned by the energy-dependent scattering parameter, remains the same as in the host polymer matrix; performance is instead dictated by polymer morphology manifested in an energy-independent transport coef?cient. We build upon this language to explain thermoelectric behavior in a variety of PEDOT and P3HT based hybrids acting as a guide for future work in multiphase materials.
关键词： polymer morphology,charge transport,PEDOT:PSS,thermoelectric materials,hybrid materials
更新于2025-09-04 15:30:14