scholarly journals High thermal conductivity states and enhanced figure of merit in aligned polymer thermoelectric materials

2021 ◽  
Author(s):  
Thibault Degousée ◽  
Viktoriia Untilova ◽  
Vishnu Vijaykumar ◽  
Xinzhao Xu ◽  
Yiwei Sun ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermoelectric Materials ◽  
Figure Of Merit ◽  
High Thermal Conductivity ◽  
Polymer Thermoelectric

Control of morphology in polymer thermoelectric materials is critical to their performance. In this work we study highly aligned polymer thermoelectric materials prepared by mechanical rubbing. We observe a remarkable...

Investigation of Thermoelectric Materials: Substitution effect of Bi on the Ag1-xPb18MTe20 (M = Sb, Bi) (x = 0, 0.14, 0.3)

2007 ◽  
Vol 1044 ◽  
Author(s):  
Mi-kyung Han ◽  
Huijun Kong ◽  
Ctirad Uher ◽  
Mercouri G Kanatzidis
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Thermoelectric Materials ◽  
Figure Of Merit ◽  
Lattice Thermal Conductivity ◽  
Substitution Effect ◽  
Dimensionless Figure Of Merit ◽  
The Matrix ◽  
Mass Fluctuation

AbstractWe performed comparative investigations of the Ag1-xPb18MTe20 (M = Bi, Sb) (x = 0, 0.14, 0.3) system to better understand the roles of Sb and Bi on the thermoelectric properties. In both systems, the electrical conductivity nearly keeps the same values, while the Seebeck coefficient decreases dramatically in going from Sb to Bi. Compared to the lattice thermal conductivity of PbTe, that of AgPb18BiTe20 is substantially reduced. The lattice thermal conductivity of the Bi analog, however, is higher than that of AgPb18SbTe20 and this is attributed largely to the decrease in the degree of mass fluctuation between the nanostructures and the matrix (for the Bi analog). As a result the dimensionless figure of merit ZT of Ag1-xPb18MTe20 (M = Bi) is found to be smaller than that of Ag1-xPb18MTe20 (M = Sb).

scholarly journals Thermoelectric Materials for Textile Applications

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3154
Author(s):  
Kony Chatterjee ◽  
Tushar K. Ghosh
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Seebeck Coefficient ◽  
Thermoelectric Materials ◽  
Figure Of Merit ◽  
Inorganic Materials ◽  
Peltier Effect ◽  
Electronic Textiles ◽  
Heating And Cooling ◽  
Recent Attention

Since prehistoric times, textiles have served an important role–providing necessary protection and comfort. Recently, the rise of electronic textiles (e-textiles) as part of the larger efforts to develop smart textiles, has paved the way for enhancing textile functionalities including sensing, energy harvesting, and active heating and cooling. Recent attention has focused on the integration of thermoelectric (TE) functionalities into textiles—making fabrics capable of either converting body heating into electricity (Seebeck effect) or conversely using electricity to provide next-to-skin heating/cooling (Peltier effect). Various TE materials have been explored, classified broadly into (i) inorganic, (ii) organic, and (iii) hybrid organic-inorganic. TE figure-of-merit (ZT) is commonly used to correlate Seebeck coefficient, electrical and thermal conductivity. For textiles, it is important to think of appropriate materials not just in terms of ZT, but also whether they are flexible, conformable, and easily processable. Commercial TEs usually compromise rigid, sometimes toxic, inorganic materials such as bismuth and lead. For textiles, organic and hybrid TE materials are more appropriate. Carbon-based TE materials have been especially attractive since graphene and carbon nanotubes have excellent transport properties with easy modifications to create TE materials with high ZT and textile compatibility. This review focuses on flexible TE materials and their integration into textiles.

Thermoelectric Generators of Sequentially Deposited Si/Si+Ge Nano-layered Superlattices

2009 ◽  
Vol 1181 ◽  
Author(s):  
Cydale Smith ◽  
Marcus Pugh ◽  
Hervie Martin ◽  
Rufus Durel Hill ◽  
Brittany James ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Thermoelectric Materials ◽  
Figure Of Merit ◽  
Rutherford Backscattering Spectrometry ◽  
Ion Beam ◽  
Absolute Temperature ◽  
Simulation Software ◽  
The Cross

AbstractEffective thermoelectric materials have a low thermal conductivity and a high electrical conductivity. The performance of the thermoelectric materials and devices is shown by a dimensionless figure of merit, ZT = S2sσ/ KTC, σ is the electrical conductivity T/KTC, where S is the Seebeck coefficient, T is the absolute temperature and KTC is the thermal conductivity. In this study we have prepared the thermoelectric generator device of Si/Si+Ge multi-layer superlattice films using the ion beam assisted deposition (IBAD). To determine the stoichiometry of the elements of Si and Ge in the grown multilayer films and the thickness of the grown multi-layer films Rutherford Backscattering Spectrometry (RBS) and RUMP simulation software package were used. The 5 MeV Si ion bombardments were performed to make quantum clusters in the multi-layer superlattice thin films to decrease the cross plane thermal conductivity, increase the cross plane Seebeck coefficient and cross plane electrical conductivity.Keywords: Ion bombardment, thermoelectric properties, multi-nanolayers, Figure of merit.

Effect of FAPAS Process on the Thermoelectric Properties of β-FeSi2

2010 ◽  
Vol 650 ◽  
pp. 137-141
Author(s):  
Qing Sen Meng ◽  
Wen Hao Fan ◽  
L.Q. Wang ◽  
L.Z. Ding
Keyword(s):  
Thermal Conductivity ◽  
Grain Size ◽  
Phase Transformation ◽  
Thermoelectric Properties ◽  
Thermoelectric Materials ◽  
Annealing Time ◽  
Figure Of Merit ◽  
Iron Disilicide ◽  
Temperature Range ◽  
Average Grain Size

Iron disilicide (-FeSi2, and -FeSi2+Cu0.1wt%) were prepared by a field-activated pressure assisted synthesis(FAPAS) method from elemental powders and the thermoelectric properties were investigated. The average grain size of these products is about 0.3m. The thermal conductivity of these materials is 3-4wm-1K-1in the temperature range 300-725K. These products’ figure of merit is 28.50×10-4 in the temperature range 330-450K. The additions of Cu promote the phase transformation of -Fe2Si5 + -FeSi → β-FeSi2 and shorten the annealing time. It is proved that FAPAS is a benign and rapid process for sintering of -FeSi2 thermoelectric materials.

Thermal Conductivity Reductions in Sige via Addition of Nanophase Particles

1994 ◽  
Vol 351 ◽  
Author(s):  
Nancy Scoville ◽  
Clara Bajger ◽  
Jon Rolfe ◽  
Jan Vandersande
Keyword(s):  
Thermal Conductivity ◽  
Thermoelectric Materials ◽  
Figure Of Merit ◽  
Erosion Process ◽  
Transport Models ◽  
Spark Erosion

ABSTRACTTransport models have predicted that the thermal conductivity of SiGe alloys could be appreciably reduced by incorporating a discrete 40Å particles with the SiGe grains. Such a thermal conductivity reduction would lead to substantial improvements in the figure-of-merit of thermoelectric materials. This paper reports on recent results on adding 40Å particles to SiGe via a spark erosion process. Thermal conductivity reductions consistent with the transport models have been achieved, however, the improvement in figure-of-merit has not been as large as predicted.

scholarly journals Transport properties in nanostructured thermoelectric materials and single crystal perovskites

2021 ◽  
Author(s):  
◽  
Michael Ng
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Single Crystal ◽  
Single Crystals ◽  
Thermoelectric Properties ◽  
Thermoelectric Materials ◽  
Ligand Exchange ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Surface Degradation

<p>Energy consumption worldwide is constantly increasing, bringing with it the demand for low cost, environmentally friendly and efficient energy technologies. One of these promising technologies is thermoelectrics in which electric power is harvested from waste heat energy. The efficiency of a thermoelectric device is determined by the dimensionless figure of merit ZT = σS²T/k where σ is the electrical conductivity, S is the thermopower, k is the thermal conductivity, and T is the average temperature. In this thesis we investigate the use of nanostructuring, which has been known to lead to significant reduction in the lattice thermal conductivity to maximise the figure of merit.  One of the most successful bulk thermoelectric materials is Bi₂Te₃, with a ZT of unity at room temperature. Here we investigate the effects of nanostructuring on the thermoelectric properties of Bi₂Te₃. Sub-100 nm ₂Te₃ nanoparticles were successfully synthesized and the figure of merit was found to be ZT ~ 5X10⁻⁵ at room temperature. The effect of a ligand exchange treatment to replace the long chain organic ligand on the as-synthesized nanoparticles with a short chain alkyl ligand was explored. After ligand exchange treatment with hydrazine the figure of merit of sub-100 nm Bi₂Te₃ was found to increase by two fold to ZT ~ 1X10⁻⁴ at room temperature. Overall the figure of merit is low compared to other nanostructured Bi₂Te₃, this was attributed to the extremely low electrical conductivity. The thermopower and thermal conductivity were found to be ~96 μVK⁻¹ and ~0.38 Wm⁻¹ K⁻¹ at 300 K respectively, which show improvements over other nanostructured Bi₂Te₃.  Further optimisation of the figure of merit was also investigated by incorporating Cu, Ni and Co dopants. The most successful of these attempts was Co in which 14.5% Co relative to Bi was successfully incorporated into sub-100 nm Bi₂Te₃. The figure of merit of nanostructured Bi₁.₇₁Co₀.₂₉Te₁.₇₁ alloy was found to increase by 40% to a ZT ~ 1.4X10⁻⁴ at room temperature. Although overall the figure of merit is low, the effect of Co alloying and hydrazine treatment shows potential as a route to optimise the figure of merit.  A potential novel material for thermoelectrics applications is inorganicorganic perovskite single crystals. Here we report a synthetic strategy to successfully grow large millimetre scale single crystals of MAPbBr₃₋xClx, FAPbBr₃₋xClx, and MAPb₁-xSnxBr₃ (MA = methylammonium and FA = formamidinium) using inverse temperature crystallisation (ITC) in a matter of days. This is the first reported case of mixed Br/Cl single crystals with a FA cation and mixed Pb/Sn based perovskites grown using ITC. The bandgap of these single crystals was successfully tuned by altering the halide and metal site composition. It was found that single crystals of FAPbBr₃₋xClx were prone to surface degradation with increased synthesis time. This surface degradation was observed to be reversible by placing the single crystals in an antisolvent such as chloroform.  A tentative model was proposed to analyse the IV characteristics of the single crystal perovskites in order to extract mobilities and diffusion lengths. The MAPbBr₃ and MAPbBr₂.₅Cl₀.₅ single crystal mobilities were found to be between 30-390 cm² V⁻¹ s⁻¹ and 10-100 cm² V⁻¹ s⁻¹ respectively, the diffusion lengths were found to be between 2-8 μm and 1-4 μm respectively. This is an improvement over polycrystalline thin film perovskites and comparable to other single crystal perovskites. The conductance of MAPb₁-xSnxBr₃ based perovskites was found to increase by 2 orders of magnitude even with just 1% of Sn incorporated. The thermal conductivity of MAPbBr₃ single crystals was found to be ~1.12 Wm⁻¹ K⁻¹ at room temperature which is reasonable low for single crystals, however no other thermoelectric properties could be measured due to the self cleaving nature of the single crystals with decreasing temperature and the high resistivity of the material.</p>

New Opportunities in Existing Thermoelectric Materials: Grain Boundary Engineering in Pulverized p-Bi2Te3 System

2007 ◽  
Vol 1044 ◽  
Author(s):  
Jian He ◽  
Xiaohua Ji ◽  
Zhe Su ◽  
Nick Gothard ◽  
Justine Edwards ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Grain Boundary ◽  
Thermoelectric Materials ◽  
Figure Of Merit ◽  
Grain Boundary Engineering ◽  
Nano Coating ◽  
Compatibility Factor ◽  
The Mean ◽  
Mean Time ◽  
Heterogeneous Layer

AbstractGrain boundary scattering provides an effective avenue to lower the thermal conductivity in polycrystalline thermoelectric materials, but it is hard to do this without simultaneously degrading the power factor that is the product of electrical conductivity and thermopower. An immediate question arises as to whether one can fabricate a thermoelectrically favorable grain boundary?In this paper we present a proof-of-principle grain boundary engineering study in the pulverized p-Bi2Te3 system. Utilizing the lately developed hydrothermal nano-coating technique, we fabricated an Alkali-metal(s)-containing surface layer with few tens of nm thick on the p-Bi2Te3 bulk reference grain, where it becomes part of the grain boundary upon hotpressing densification. The electrical resistivity, thermopower, thermal conductivity and Hall coefficient measurements constitute solid evidence that this heterogeneous layer helps decouple the otherwise inter-related resistivity, thermopower and thermal conductivity. To optimize the figure of merit ZT, we carefully varied the ratio between Na, K and Rb concentrations. It was found that the sample treated in the solution with Na/Rb =1:2 achieved a ZT comparable with that of the commercial ingot; in the mean time, the compatibility factor and robustness of device were considerably improved. In principle this technique can be applied to other existing polycrystalline thermoelectric materials as a new “tuning knob”.

On The Thermoelectric Power And Transport Properties Of Quasicrystals

1998 ◽  
Vol 553 ◽  
Author(s):  
F. Cyrot-Lackmann
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Fermi Surface ◽  
Physical Properties ◽  
Thermoelectric Power ◽  
Thermoelectric Materials ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Phonon Drag ◽  
Crude Estimate

Stable quasicrystals exhibit specific and unusual physical properties, such as, diamagnetism, low electrical conductivity, low thermal conductivity, and large themoelectric power at room temperature. These properties can be understood with a Bragg's reflexions scheme due to their dense filled reciprocal space.This leads to small gaps on the Fermi surface (some tenths of eV), much narrower than the usual Hume-Rothery ones (of order of 0.5 eV) which explain their stability. These gaps lead to the existence of quasi Umklapp processes, crucial for the interpretation of thermoelectric power. In some cases, the positive phonon drag contribution due to Umklapp processes, add with the electronic one's and dominates at room temperature with a large positive thermoelectric power. A crude estimate of the figure of merit gives some hope for applications of some quasicrystals and high approximants as new thermoelectric materials.

COMPARISON OF HARMAN AND COOLING COUPLE METHODS FOR Z DETERMINATION

1966 ◽  
Vol 44 (5) ◽  
pp. 971-985 ◽  
Author(s):  
W. B. Muir
Keyword(s):  
Thermal Conductivity ◽  
Electrical Resistivity ◽  
Temperature Difference ◽  
Thermoelectric Materials ◽  
Figure Of Merit ◽  
Maximum Temperature ◽  
Maximum Temperature Difference ◽  
Type Apparatus

A Peltier–Seebeck or Harman type apparatus has been constructed to measure the Seebeclc coefficient, α, thermal conductivity, κ, electrical resistivity, ρ, and the figure of merit, Z, of thermoelectric materials over the range of temperature 150–300 °K while maintaining the sample in an approximately isothermal environment. Errors in the measured values of ρ, Z, α, and κ have been kept within 1, 1.5, 3, and 5% respectively. A comparison of the maximum temperature difference, ΔTmax, measured in a cooling test and the value of ΔTmax calculated from the values of α, κ, and ρ as a function of temperature measured in the Harman apparatus shows that, for five thermocouples, agreement is obtained within 1.2 °K on the average, with the greatest disparity being 2.5 °K.

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