The Influence of Silicon Dopant and Processing on Thermoelectric Properties of B4C Ceramics

1998 ◽  
Vol 545 ◽  
Author(s):  
Ke-Feng Cai ◽  
Ce-Wen Nan ◽  
Xin-Min Min
Keyword(s):  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Thermoelectric Properties ◽  
Hot Pressing ◽  
Figure Of Merit ◽  
Room Temperature ◽  
A Value ◽  
Si Doped

AbstractB4C ceramics doped with various content of Si (0 to 2.03 at%) are prepared via hot pressing. The composition and microstructure of the ceramics are characterized by means of XRD and EPMA. Their electrical conductivity and Seebeck coefficient of the samples are measured from room temperature up to 1500K. The electrical conductivity increases with temperature, and more rapidly after 1300K; the Seebeck coefficient of the ceramics also increases with temperature and rises to a value of about 320μVK−1. The value of the figure of merit of Si-doped B4C rises to about 4 × 10−4K−1 at 1500K.

Thermoelectric Properties of n-type (Bi2Se3)x(Bi2Te3)1-x Crystals Prepared by Zone Melting

2008 ◽  
Vol 368-372 ◽  
pp. 547-549
Author(s):  
Jun Jiang ◽  
Ya Li Li ◽  
Gao Jie Xu ◽  
Ping Cui ◽  
Li Dong Chen
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Carrier Concentration ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Zone Melting ◽  
Chemical Compositions ◽  
Melting Method ◽  
Temperature Range

In the present study, n-type (Bi2Se3)x(Bi2Te3)1-x crystals with various chemical compositions were fabricated by the zone melting method. Thermoelectric properties, including Seebeck coefficient (α), electrical conductivity (σ) and thermal conductivity (κ), were measured in the temperature range of 300-500 K. The influence of the variations of Bi2Te3 and Bi2Se3 content on thermoelectric properties was studied. The increase of Bi2Se3 content (x) caused an increase in carrier concentration and thus an increase of σ and a decrease of α. The maximum figure of merit (ZT = α2σT/κ) of 0.87 was obtained at about 325 K for the composition of 93%Bi2Te3-7%Bi2Se3 with doping TeI4.

Tuning the thermoelectric properties of a single-molecule junction by mechanical stretching

2015 ◽  
Vol 17 (7) ◽  
pp. 5386-5392 ◽  
Author(s):  
Alberto Torres ◽  
Renato B. Pontes ◽  
Antônio J. R. da Silva ◽  
Adalberto Fazzio
Keyword(s):  
Seebeck Coefficient ◽  
Thermoelectric Properties ◽  
Single Molecule ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Heat Conductance ◽  
Molecule Junction ◽  
Electronic Heat ◽  
Single Molecule Junction ◽  
Mechanical Stretching

We theoretically investigate, as a function of the stretching, the behaviour of the Seebeck coefficient, the electronic heat conductance and the figure of merit of a molecule-based junction composed of a benzene-1,4-dithiolate (BDT) molecule coupled to Au(111) surfaces at room temperature.

scholarly journals Enhanced Thermoelectric Properties of WS2/Single-Walled Carbon Nanohorn Nanocomposites

Crystals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 140 ◽  
Author(s):  
Ji Hoon Kim ◽  
Seunggun Yu ◽  
Sang Won Lee ◽  
Seung-Yong Lee ◽  
Keun Soo Kim ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Thermoelectric Properties ◽  
High Frequency ◽  
Figure Of Merit ◽  
Thermoelectric Efficiency ◽  
Thermoelectric Figure ◽  
Carbon Nanohorns ◽  
Single Walled Carbon ◽  
High Frequency Induction

Recently, two-dimensional tungsten disulfide (WS2) has attracted attention as a next generation thermoelectric material due to a favorable Seebeck coefficient. However, its thermoelectric efficiency still needs to be improved due to the intrinsically low electrical conductivity of WS2. In the present study, thermoelectric properties of WS2 hybridized with highly conductive single-walled carbon nanohorns (SWCNHs) were investigated. The WS2/SWCNH nanocomposites were fabricated by annealing the mixture of WS2 and SWCNHs using a high-frequency induction heated sintering (HFIHS) system. By adding SWCNHs to WS2, the nanocomposites exhibited increased electrical conductivity and a slightly decreased Seebeck coefficient with the content of SWCNHs. Hence, the maximum power factor of 128.41 μW/mK2 was achieved for WS2/SWCNHs with 0.1 wt.% SWCNHs at 780 K, resulting in a significantly improved thermoelectric figure of merit (zT) value of 0.027 compared to that of pristine WS2 with zT 0.017.

Synthesis and Thermoelectric Properties of Co4-XFeXSb12-YSnY Skutterudites

2011 ◽  
Vol 695 ◽  
pp. 65-68 ◽  
Author(s):  
Kwan Ho Park ◽  
Il Ho Kim
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Phonon Scattering ◽  
Charge Compensation ◽  
Fe Doping ◽  
Sn Doping ◽  
Double Doping

Co4-xFexSb12-ySny skutterudites were synthesized by mechanical alloying and hot pressing, and thermoelectric properties were examined. The carrier concentration increased by doping and thereby the electrical conductivity increased compared with intrinsic CoSb3. Every specimen had a positive Seebeck coefficient. Fe doping caused a decrease in the Seebeck coefficient but it could be enhanced by Fe/Sn double doping possibly due to charge compensation. The thermal conductivity was desirably very low and this originated from ionized impurity-phonon scattering. Thermoelectric properties were improved remarkably by Fe/Sn doping, and a maximum figure of merit, ZT = 0.5 was obtained at 723 K in the Co3FeSb11.2Sn0.8 specimen.

Thermoelectric Properties of YbBiPt and YBiPt Thin Films

2008 ◽  
Vol 1100 ◽  
Author(s):  
Sadik Guner ◽  
Satilmis Budak ◽  
Claudiu I Muntele ◽  
Daryush Ila
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Rutherford Backscattering Spectrometry ◽  
Conductivity Measurement ◽  
Electronic Energy ◽  
Before And After

AbstractMonolayer thin films of YbBiPt and YBiPt have been produced with 560 nm and 394 nm thick respectively in house and their thermoelectric properties were measured before and after MeV ion bombardment. The energy of the ions were selected such that the bombarding Si ions stop in the silicon substrate and deposit only electronic energy by ionization in the deposited thin film. The bombardment by 5.0 MeV Si ions at various fluences changed the homogeneity as well as reducing the internal stress in the films thus affecting the thermal, electrical and Seebeck coefficient of thin films. The stoichiometry of the thin films was determined using Rutherford Backscattering Spectrometry, the thickness has been measured using interferometry and the electrical conductivity was measured using Van der Pauw method. Thermal conductivity of the thin films was measured using an in-house built 3ω thermal conductivity measurement system. Using the measured Seebeck coefficient, thermal conductivity and electrical conductivity we calculated the figure of merit (ZT). We will report our findings of change in the measured figure of merit as a function of bombardment fluence.

Effect of Nanocavities on the Thermoelectric Properties of Polycrystalline Silicon

2011 ◽  
Vol 1329 ◽  
Author(s):  
Ekaterina Selezneva ◽  
Andrea Arcari ◽  
Gilles Pernot ◽  
Elisabetta Romano ◽  
Gianfranco Cerofolini ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Thermoelectric Properties ◽  
Polycrystalline Silicon ◽  
Figure Of Merit ◽  
Annealing Temperature ◽  
Silicon Films ◽  
Negative Effect ◽  
Polycrystalline Silicon Films

ABSTRACTNanostructuring has opened new ways to increase the thermoelectric performance of a host of materials, mainly by decreasing their thermal conductivity κ while preserving the Seebeck coefficient S and electrical conductivity σ. The thermoelectric properties of degenerated polycrystalline silicon films with nanocavities (NCs) have been studied as a function of annealing temperature upon isochronous annealings in argon carried out every 50°C in the range 500 – 1000°C which were used to modify the shape of the NCs. We found that presence of the NCs had no negative effect on the electronic properties of the system. The measured values of S and σ were close to those previously reported for the blank polycrystalline silicon films with the same doping level. The thermal conductivity was also found to be close to the value measured on the blank sample, about half of the reported value in polycrystals. This led to a power factor of 15.2 mWm-1K-2 and a figure of merit of 0.18 at 300 K.

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.

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>

Enhancement of Thermoelectric Properties of P3HT by Addition of Carbon Nanotubes

2019 ◽  
pp. 59-77
Author(s):  
Arif ◽  
Muhammad Tahir ◽  
Hijaz Ahmad
Keyword(s):  
Thin Film ◽  
Carbon Nanotubes ◽  
Electrical Conductivity ◽  
Renewable Energy ◽  
Thermoelectric Properties ◽  
Material Characterization ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Casting Technique ◽  
Semiconducting Material

In this paper, the enhancement in the thermoelectric properties of the organic semiconducting material, poly(3-hexylthiophene) (P3HT) by addition of carbon nanotubes (CNTs), have been studied for applications in the renewable energy. For this purpose, the thin film of P3HT: CNTs blend has been deposited on the glass substrate by drop casting technique. The blend is prepared by the ratio of 10: 0.5 mg of P3HT: CNTs at room temperature in chloroform. The thickness of P3HT: CNTs nanocomposite found by ellipsometer was 2570 nm. The Seebeck coefficient of the film is measured to be 58.18 mV/K and the electrical conductivity of nanocomposite was 254 S/cm found by four probe method. The bandgap of P3HT: CNTs nanocomposite was 1.4 eV measured by UV-Vis spectrometer. In this blend, the CNTs are used for enhancement of the thermoelectric properties of the film. The films are also characterized by different material characterization techniques. These characterizations are correlated with the thermoelectric properties of the material. The optimized value of the figure of merit (ZT) for the thin film has been achieved ZT = 0.14 for the P3HT: CNTs nanocomposites.

Preparation and Thermoelectric Properties of Bi-Doped Mg2Si Nanocomposites

2009 ◽  
Vol 66 ◽  
pp. 17-20 ◽  
Author(s):  
Mei Jun Yang ◽  
Wei Jun Luo ◽  
Qiang Shen ◽  
Hong Yi Jiang ◽  
Lian Meng Zhang
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Dimensionless Figure Of Merit ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Heavy Doping ◽  
Nanocomposite Structures

Nanocomposites and heavy doping both are regarded as effective way to improve materials’ thermoelectric properties. 0.7at% Bi-doped Mg2Si nanocomposites were prepared by spark plasma sintering. Results of thermoelectric properties tests show that the doping of Bi atom effectively improves the electrical conductivity of Mg2Si，and the nanocomposite structures are helpful to reduce thermal conductivity and increase Seebeck coefficient, hence improving the thermoelectric performance. A maximum dimensionless figure of merit of 0.8 is obtained for the Bi-doped Mg2Si nanocomposite with 50 wt % nanopowder inclusions at 823K, about 63% higher than that of Bi-doped Mg2Si sample without nanopowder inclusions and 119% higher than that of microsized Mg2Si sample without Bi-doped, respectively.

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