Imaging Thermoelectric Properties at the Nanoscale.
Ontology highlight
ABSTRACT:
SUBMITTER: Grauby S
PROVIDER: S-EPMC8147288 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:Electron-doped SrTiO3 is a well-known n-type thermoelectric material, although the figure of merit of SrTiO3 is still inferior compared with p-type metal oxide-based thermoelectric materials due to its high lattice thermal conductivity. In this study, we have used a different amount of the non-ionic surfactant F127 during sample preparation to introduce nanoscale porosities into bulk samples of La-doped SrTiO3. It has been observed that the porosities introduced into the bulk sample significantly improve the Seebeck coefficient and reduce the thermal conductivity by the charge carrier and phonon scattering respectively. Therefore, there is an overall enhancement in the power factor (PF) followed by a dimensionless figure of merit (zT) over a wide scale of temperature. The sample 20 at% La-doped SrTiO3 with 600 mg of F127 surfactant (SLTO 600F127) shows the maximum PF of 1.14 mW m-1 K-2 at 647 K which is 35% higher than the sample without porosity (SLTO 0F127), and the same sample (SLTO 600F127) shows the maximum value of zT is 0.32 at 968 K with an average enhancement of 62% in zT in comparison with the sample without porosity (SLTO 0F127).
| S-EPMC6837226 | biostudies-literature
Project description:A layered Zintl antimonide NaZnSb (PbClF or Cu?Sb structure type; P4/nmm) was synthesized using the reactive sodium hydride NaH precursor. This method provides comprehensive compositional control and facilitates the fast preparation of high-purity samples in large quantities. NaZnSb is highly reactive to humidity/air and hydrolyzes to NaOH, ZnO, and Sb in aerobic conditions. On the other hand, NaZnSb is thermally stable up to 873 K in vacuum, as no structural changes were observed from high-temperature synchrotron powder X-ray diffraction data in the 300?873 K temperature range. The unit cell expansion upon heating is isotropic; however, interatomic distance elongation is not isotropic, consistent with the layered structure. Low- and high-temperature thermoelectric properties were measured on pellets densified by spark plasma sintering. The resistivity of NaZnSb ranges from 11 m??cm to 31 m??cm within the 2?676 K range, consistent with heavily doped semiconductor behavior, with a narrow band gap of 0.23 eV. NaZnSb has a large positive Seebeck coefficient (244 ?V?K-1 at 476 K), leading to the maximum of zT of 0.23 at 675 K. The measured thermoelectric properties are in good agreement with those predicted by theoretical calculations.
| S-EPMC6337516 | biostudies-literature
Project description:SnTe has been the focus of numerous experimental and theoretical studies over the last years owing to its high thermoelectric performances near 800 K when appropriately doped. Here, we demonstrate that melt-spinning, an ultrafast-quenching synthesis technique, followed by spark plasma sintering results in enhanced ZT values in polycrystalline SnTe. To illustrate the impact of this technique, the results are contrasted with those obtained on two polycrystalline samples prepared by direct quenching of molten SnTe and without quenching. SnTe melt-spun ribbons are characterized by a peculiar columnar microstructure that contributes to lower the lattice thermal conductivity below 700 K in pressed samples. More importantly, this technique results in a significant decrease in the hole concentration, giving rise to enhanced thermopower values above 500 K. The variation in the hole concentration is likely due to a slight loss of elemental Te during the melt-spinning process. Thanks to the decreased hole concentration, the thermoelectric performances are significantly enhanced with a peak ZT value of 0.6 at 800 K, which represents a 40% increase over the values measured for samples prepared with and without quenching. These findings indicate that melt-spinning provides a novel strategy to improve the thermoelectric properties of SnTe that could be worthwhile extending to substituted compounds.
| S-EPMC6645241 | biostudies-literature
Project description:We have combined ultrasensitive magnetic resonance force microscopy (MRFM) with 3D image reconstruction to achieve magnetic resonance imaging (MRI) with resolution <10 nm. The image reconstruction converts measured magnetic force data into a 3D map of nuclear spin density, taking advantage of the unique characteristics of the "resonant slice" that is projected outward from a nanoscale magnetic tip. The basic principles are demonstrated by imaging the (1)H spin density within individual tobacco mosaic virus particles sitting on a nanometer-thick layer of adsorbed hydrocarbons. This result, which represents a 100 million-fold improvement in volume resolution over conventional MRI, demonstrates the potential of MRFM as a tool for 3D, elementally selective imaging on the nanometer scale.
| S-EPMC2628306 | biostudies-literature
Project description:A remarkable decrease in the lattice thermal conductivity and enhancement of thermoelectric figure of merit were recently observed in rock-salt cubic SnTe, when doped with germanium (Ge). Primarily, based on theoretical analysis, the decrease in lattice thermal conductivity was attributed to local ferroelectric fluctuations induced softening of the optical phonons which may strongly scatter the heat carrying acoustic phonons. Although the previous structural analysis indicated that the local ferroelectric transition temperature would be near room temperature in [Formula: see text], a direct evidence of local ferroelectricity remained elusive. Here we report a direct evidence of local nanoscale ferroelectric domains and their switching in [Formula: see text] using piezoeresponse force microscopy(PFM) and switching spectroscopy over a range of temperatures near the room temperature. From temperature dependent (250-300 K) synchrotron X-ray pair distribution function (PDF) analysis, we show the presence of local off-centering distortion of Ge along the rhombohedral direction in global cubic [Formula: see text]. The length scale of the [Formula: see text] off-centering is 0.25-0.10 Å near the room temperatures (250-300 K). This local emphatic behaviour of cation is the cause for the observed local ferroelectric instability, thereby low lattice thermal conductivity in [Formula: see text].
| S-EPMC8387443 | biostudies-literature
Project description:The pentagon has been proven to be an important structural unit for carbon materials, leading to different physical and chemical properties from those of hexagon-based allotropes. Following the development from graphene to penta-graphene, a breakthrough has very recently been made for graphyne-for example, imidazole-graphyne (ID-GY) was formed by assembling experimentally synthesized pentagonal imidazole molecules and acetylenic linkers. In this work, we study the thermal properties and thermoelectric performance of ID-GY by combining first principle calculations with the Boltzmann transport theory. The calculated lattice thermal conductivity of ID-GY is 10.76 W/mK at 300 K, which is only one tenth of that of γ-graphyne (106.24 W/mK). A detailed analysis of the harmonic and anharmonic properties, including the phonon group velocity, phonon lifetime, atomic displacement parameter, and bond energy curves, reveals that the low lattice thermal conductivity can be attributed to the low Young's modulus, low Debye temperature, and high Grüneisen parameter. Furthermore, at room temperature, ID-GY can reach a high ZT value of 0.46 with a 5.8 × 1012 cm-2 hole concentration, which is much higher than the value for many other carbon-based materials. This work demonstrates that changing structural units from hexagonal to pentagonal can significantly reduce the lattice thermal conductivity and enhance the thermoelectric performance of carbon-based materials.
| S-EPMC8509738 | biostudies-literature
Project description:Tin selenide (SnSe) has been the subject of great attention in the last years due to its highly efficient thermoelectricity and its possibilities as a green material, free of Pb and Te. Here, we report for the first time a thermoelectricity and transport study of individual SnSe micro- and nano-wires with diameters in the range between 130 nm and 1.15 μm. X-ray diffraction and transmission electron microscopy analyses confirm an orthorhombic SnSe structure with Pnma (62) symmetry group and 1:1 Sn:Se atomic ratio. Electrical and thermal conductivity and the Seebeck coefficient were measured in each individual nanowire using a specialized suspended microdevice in the 150-370 K temperature range, yielding a thermal conductivity of 0.55 Wm-1 K-1 at room temperature and ZT ~ 0.156 at 370 K for the 130 nm diameter nanowire. The measured properties were correlated with electronic information obtained by model simulations and with phonon scattering analysis. The results confirm these structures as promising building blocks to develop efficient temperature sensors, refrigerators and thermoelectric energy converters. The thermoelectric response of the nanowires is compared with recent reports on crystalline, polycrystalline and layered bulk structures.
| S-EPMC6086875 | biostudies-literature
Project description:Rare-earth (RE) tellurides have been studied extensively for use in high-temperature thermoelectric applications. Specifically, lanthanum and praseodymium-based compounds with the Th₃P₄ structure type have demonstrated dimensionless thermoelectric figures of merit (zT) up to 1.7 at 1200 K. Scandium, while not part of the lanthanide series, is considered a RE element due to its chemical similarity. However, little is known about the thermoelectric properties of the tellurides of scandium. Here, we synthesized scandium sesquitelluride (Sc₂Te₃) using a mechanochemical approach and formed sintered compacts through spark plasma sintering (SPS). Temperature-dependent thermoelectric properties were measured from 300⁻1100 K. Sc₂Te₃ exhibited a peak zT = 0.3 over the broad range of 500⁻750 K due to an appreciable power factor and low-lattice thermal conductivity in the mid-temperature range.
| S-EPMC6427805 | biostudies-other
Project description:Weyl semimetals are a new class of topological materials possessing outstanding physical properties. We investigate the thermoelectric properties of a ballistic Weyl semimetal specimen connected to two normal contacts. We introduce a model to evaluate the thermoelectric coefficients of the junction and analyze its features along two distinct directions, one along the chiral axis of the Weyl semimetal and the other perpendicular to it. We demonstrate that the thermoelectric response of this junction depends on whether it is along the chiral axis of the Weyl semimetal or not. Electrical and thermal conductances of this junction reveal considerable dependence on the length and chemical potential of the Weyl semimetal layer. In particular, we observe that, decreasing the chemical potential in the normal contacts enhances the Seebeck coefficient and thermoelectric figure of merit of the junction to substantial values. Hence, we unveil that a ballistic junction of Weyl semimetal can serve as a fundamental segment for application in future thermoelectric devices for thermal energy harvesting.
| S-EPMC10471620 | biostudies-literature
Project description:Co-expression of a specific group of genes requires physical associations among these genes, which form functional chromosomal contacts. While DNA fluorescence in situ hybridization (FISH) pinpoints the localization of genes within the 3D nuclear architecture, direct evidence of physical chromosomal contacts is still lacking. Here, we report a method for the direct visualization of transcription-dependent chromosomal contacts formed in two distinct mechanical states of cells. We prepared open chromatin spreads from isolated nuclei, ensuring 2D rendering of chromosome organization. Superresolution imaging of these chromatin spreads resolved the nanoscale organization of genome contacts. We optimized our imaging method using chromatin spreads from serum+/- cells. We then showed direct visualization of functional gene clusters targeted by YAP (Yes-associated protein) and SRF (Serum response factor) transcription factors. In addition, we showed the association of NF-?B bound gene clusters induced by TNF-? addition. Furthermore, EpiTect ChIP qPCR results showed that these nanoscale clusters were enriched with corresponding transcription factors. Taken together, our method provides a robust platform to directly visualize and study specific genome-wide chromosomal contacts.
| S-EPMC5301241 | biostudies-literature