scholarly journals Microwave Irradiation to Produce High Performance Thermoelectric Material Based on Al Doped ZnO Nanostructures

Crystals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 610
Author(s):  
Neazar Baghdadi ◽  
Numan Salah ◽  
Ahmed Alshahrie ◽  
Kunihito Koumoto
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Microwave Irradiation ◽  
High Performance ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Zno Nanostructures ◽  
Al Doping ◽  
Doped Zno ◽  
Te Material

Microwave irradiation is found to be effective to provide highly crystalline nanostructured materials. In this work, this technique has been used to produce highly improved thermoelectric (TE) material based on aluminum (Al) doped zinc oxide (ZnO) nanostructures (NSs). The effect of Al dopant at the concentration range 0.5–3 mol % on the structural and TE properties has been investigated in more details. The optimum concentration of Al for better TE performance is found to be 2 mol %, which could significantly increase the electrical conductivity and reduce the thermal conductivity of ZnO NSs and thus enhance the TE performance. This concentration showed almost metallic conductivity behavior for ZnO NSs at low temperatures, e.g., below 500 K. The electrical conductivity reached 400 S/m at room temperature, which is around 200 times greater than the value recorded for the pure ZnO NSs. Remarkably, the measured room temperature thermal conductivity of the microwave synthesized ZnO NSs was very low, which is around 4 W/m·K. This value was further reduced to 0.5 W/m·K by increasing the Al doping to 3 mol %. The figure of merit recorded 0.028 at 675 K, which is 15 times higher than that of the pure ZnO NSs. The output power of a single leg module made of 2 mol % Al doped ZnO NSs was 3.7 µW at 485 K, which is higher by 8 times than that of the pure sample. These results demonstrated the advantage of the microwave irradiation rout as a superior synthetic technique for producing and doping promising TE nanomaterials like ZnO NSs.

Thermoelectric Properties of Binary-Phased Nanocomposites

2014 ◽  
Vol 809-810 ◽  
pp. 3-8
Author(s):  
Peng Xian Lu
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Hot Press ◽  
Point Temperature ◽  
Disordered Structure ◽  
Maximum Value ◽  
Hot Press Process

In order to increase the electrical conductivity greatly but maintain a large Seebeck coefficient and a low thermal conductivity simultaneously, the binary-phased LaCeFe3CoSb12-Sb nanocomposites composed of LaCeFe3CoSb12skutterudite nanospheres and semimetal Sb microsized ribbons were fabricated via a hydro/solvo thermal route. The results suggest that the Sb powders result in a disordered structure during a hot-press process at its melting-point temperature and the disordered structure has been partly preserved into the room-temperature materials successfully. The Sb microsized ribbons enhance the electrical conductivity of the binary-phased materials largely, meanwhile the disordered structure increases the Seebeck coefficient obviously even though the thermal conductivity is also increased slightly. Consequently, the figure of merit of the binary-phased materials is improved significantly and the maximum value of 1.54 at 773 K has been realized for the LaCeFe3CoSb15material.

Synthesis and thermoelectric properties of tantalum-doped ZrNiSn half-Heusler alloys

2014 ◽  
Vol 07 (03) ◽  
pp. 1450032 ◽  
Author(s):  
Degang Zhao ◽  
Min Zuo ◽  
Zhenqing Wang ◽  
Xinying Teng ◽  
Haoran Geng
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Acoustic Phonon ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Phonon Scattering ◽  
Heusler Alloys ◽  
Hot Press ◽  
Arc Melting ◽  
Hot Press Sintering

The Ta -doped ZrNiSn half-Heusler alloys, Zr 1-x Ta x NiSn , were synthesized by arc melting and hot-press sintering. Microstructure of Zr 1-x Ta x NiSn compounds were analyzed and the thermoelectric (TE) properties of Zr 1-x Ta x NiSn compounds were measured from room temperature to 823 K. The electrical conductivity increased with increasing Ta content. The Seebeck coefficient of Zr 1-x Ta x NiSn compounds was sharply decreased with increasing Ta content. The Hall mobility was proportional to T-1.5 above 673 K, indicating that the acoustic phonon scattering was predominant in the temperature range. The thermal conductivity was effectively depressed by introducing Ta substitution. The figure of merit of ZrNiSn compounds was improved due to the decreased thermal conductivity and increased electrical conductivity. The maximum ZT value of 0.60 was achieved for Zr 0.97 Ta 0.03 NiSn sample at 823 K.

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>

Raising the Thermoelectric Performance of Fe3CoSb12 Skutterudites via Nd Filling and In-Situ Nanostructuring

2016 ◽  
Vol 16 (4) ◽  
pp. 3841-3847 ◽  
Author(s):  
Lijie Guo ◽  
Zhengwei Cai ◽  
Xiaolong Xu ◽  
Kunling Peng ◽  
Guiwen Wang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Thermoelectric Performance ◽  
Large Reduction ◽  
Dimensionless Figure Of Merit ◽  
Plasma Sintering ◽  
Spark Plasma

p-type skutterudites NdxFe3CoSb12 with x equaling 0.8, 0.85, 0.9, 0.95, 1.0 have been synthesized by solid state reaction followed by spark plasma sintering. The influence of Nd filling on electrical and thermal transport properties has been investigated in the Nd-filled skutterudite compounds in the temperature range from room temperature to 800 K. It was found that the Seebeck coefficient is drastically enhanced via filling Nd in p-Type skutterudites as well as the corresponding power factor although electrical conductivity is reduced. In addition, a large reduction in thermal conductivity is achieved by Nd fillers through rattling effect along with the In-Situ nanostructured precipitate through scattering phonons with much wider frequency. These concomitant effects result in an enhanced thermoelectric performance with the dimensionless figure of merit ZT. These observations demonstrate an exciting scientific opportunity to raise the figure-of-merit of p-type skutterudites.

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.

Annealing Effect on the Thermoelectric Properties of Hot Extruded Bi2(Te0.94Se0.06)3+0.07wt%I+0.03wt%CuBr+0.02wt%Te Compound

2006 ◽  
Vol 15-17 ◽  
pp. 404-409
Author(s):  
Wang Kee Min ◽  
Sung Doo Hwang ◽  
Chang Ho Lee ◽  
Young Do Park ◽  
Yang Do Kim ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Annealing Temperature ◽  
Raw Materials ◽  
Extrusion Process ◽  
Annealing Process ◽  
Annealing Effect ◽  
Z Value

The n-type Bi2(Te0.94Se0.06)3 thermoelectric compound was prepared by the direct extrusion process using the powder as raw materials. Hot extruded specimens were annealed at 200°C and 350°C for 2hrs. The electrical conductivity, thermoelectric power and thermal conductivity of hot extruded and annealed specimens were measured at room temperature. The fractographs of the specimens showed that the grain size became coarser and a lot of porosities were generated during annealing process. The power factor value (PF) decreased with increasing the annealing temperature. The electric conductivity and thermal conductivity of the specimens also decreased with the increase of annealing temperature. This may be reasoned that the generated porosities affect the thermal conductivity of the specimens prepared in this study. The figure of merit (Z) value of the annealed specimens at 350°C was improved about 10%. The highest Z value of the specimens annealed at 350°C was 2.0 x 10-3/K among the prepared specimens.

scholarly journals Structural Modularization of Cu2Te Leading to High Thermoelectric Performance near the Mott-Ioffe-Regel Limit

2021 ◽  
Author(s):  
Kunpeng Zhao ◽  
Chenxi Zhu ◽  
Min Zhu ◽  
Hongyi Chen ◽  
Jindan Lei ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Energy Conversion ◽  
Thermoelectric Materials ◽  
High Performance ◽  
Figure Of Merit ◽  
Rational Design ◽  
Absolute Temperature ◽  
Band Edge ◽  
Total Thermal Conductivity ◽  
Te Material

Abstract To date, thermoelectric materials research stays focused on optimizing the material’s band edge details and disfavors low mobility. Here, we shifts the paradigm from the band edge to the mobility edge, exploring high thermoelectricity near the border of band conduction and hopping. Through co-alloying iodine and sulfur, we modularize the plain crystal structure of liquid-like thermoelectric material Cu2Te with mosaic nanodomains and the highly size mismatched S/Te sublattice that chemically quenches the Cu sublattice and drives the electronic states from itinerant to localized. A state-of-the-art figure of merit of 1.4 is obtained at 850 K for Cu2(S0.4I0.1Te0.5); and remarkably, it is achieved near the Mott-Ioffe-Regel limit unlike mainstream thermoelectric materials that are band conductors. Broadly, pairing structural modularization with the high performance near the Mott-Ioffe-Regel limit paves an important new path towards the rational design of high-performance thermoelectric materials. Thermoelectric (TE) material-based energy conversion technology has attracted increasing global attention in virtue of the technical merits such as no moving parts, no greenhouse emission, noiseless, friendliness for miniaturization, and reliability.1–4 Based on the Seebeck and Peltier effects, thermoelectricity enables a direct energy conversion between temperature difference and electricity.5, 6 The performance of a TE material is primarily gauged by the material’s figure of merit, zT = S2T/ρκ, where S is the Seebeck coefficient, T is the absolute temperature, ρ is the electrical resistivity, and κ is the total thermal conductivity (consisting of the lattice thermal conductivity κL and the electronic thermal conductivity κE).

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>

scholarly journals Local ferroelectric polarization switching driven by nanoscale distortions in thermoelectric $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Aastha Vasdev ◽  
Moinak Dutta ◽  
Shivam Mishra ◽  
Veerpal Kaur ◽  
Harleen Kaur ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Lattice Thermal Conductivity ◽  
Direct Evidence ◽  
Temperature Dependent ◽  
Force Microscopy ◽  
Ferroelectric Domains ◽  
Pdf Analysis ◽  
Ferroelectric Transition Temperature

AbstractA 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 $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te , a direct evidence of local ferroelectricity remained elusive. Here we report a direct evidence of local nanoscale ferroelectric domains and their switching in $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te 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 $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te . The length scale of the $${\text {Ge}}^{2+}$$ Ge 2 + 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 $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te .

scholarly journals Decoupling electron and phonon transport in single-nanowire hybrid materials for high-performance thermoelectrics

2021 ◽  
Vol 7 (20) ◽  
pp. eabe6000
Author(s):  
Lin Yang ◽  
Madeleine P. Gordon ◽  
Akanksha K. Menon ◽  
Alexandra Bruefach ◽  
Kyle Haas ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Transport ◽  
Electrical Transport ◽  
High Performance ◽  
Figure Of Merit ◽  
Phonon Transport ◽  
Core Shell ◽  
Nanowire Diameter ◽  
High Performing ◽  
Polycrystalline Thin Films

Organic-inorganic hybrids have recently emerged as a class of high-performing thermoelectric materials that are lightweight and mechanically flexible. However, the fundamental electrical and thermal transport in these materials has remained elusive due to the heterogeneity of bulk, polycrystalline, thin films reported thus far. Here, we systematically investigate a model hybrid comprising a single core/shell nanowire of Te-PEDOT:PSS. We show that as the nanowire diameter is reduced, the electrical conductivity increases and the thermal conductivity decreases, while the Seebeck coefficient remains nearly constant—this collectively results in a figure of merit, ZT, of 0.54 at 400 K. The origin of the decoupling of charge and heat transport lies in the fact that electrical transport occurs through the organic shell, while thermal transport is driven by the inorganic core. This study establishes design principles for high-performing thermoelectrics that leverage the unique interactions occurring at the interfaces of hybrid nanowires.

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