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1.
《理论物理通讯》2015,(9)
The thermoelectric properties of a benzene molecule coupled to three-dimensional metallic electrodes are examined in the presence of dephasing processes using Green function formalism in the linear response regime. The three different kind of configurations(ortho, meta and para) are taken into account for the coupling between the molecule and electrodes. Results show that the thermoelectric properties of the single molecular junction are strongly dependent on the coupling geometry. Our results predict that the thermoelectric efficiency is increased in specific geometry as a consequence of interference effects. It is found that the dephasing effects result in the reduction of the thermoelectric efficiency. 相似文献
2.
Thermoelectric power generators require high-efficiency thermoelectric materials to transform waste heat into usable electrical energy. An efficient thermoelectric material should have high Seebeck coefficient and excellent electrical conductivity as well as low thermal conductivity. Graphene, the first truly 2D nanomaterial, exhibits unique properties which suit it for use in thermoelectric power generators, but its application in thermoelectrics is limited by the high thermal conductivity and low Seebeck coefficient resulting from its gapless spectrum. However, with the possibility of modification of graphene's band structure to enhance Seebeck coefficient and the reduction of its thermal conductivity, it is an exciting prospect for application in thermoelectric power generation. This article examines the electronic, optical, thermal, and thermoelectric properties of graphene systems. The factors that contribute to these material properties in graphene systems like charge carriers scattering mechanisms are discussed. A salient aspect of this article is a synergistic perspective on the reduction of thermal conductivity and improvement of Seebeck coefficient of graphene for a higher thermoelectric energy conversion efficiency. In this regard, the effect of graphene nanostructuring and doping, forming of structural defects, as well as graphene integration into a polymer matrix on its thermal conductivity and Seebeck coefficient is elucidated. 相似文献
3.
N. S. Popovich 《Czechoslovak Journal of Physics》2005,55(6):739-748
High efficiency of thermoelectric conversion can be achieved by using materials with a high Seebeck coefficient, high electrical conductivity, and low thermal conductivity. Mass-difference-scattering of the phonons is one of the most effective way for reducing the thermal conductivity in bulk thermoelectric materials. Investigations of transport phenomena in (TlBiS2)1-x
(2PbS)x alloys system have shown that in solid solutions of the (A3B5C
2
6
)1-x
(2A4B6)x type at cation substitution according to scheme 2A4(+2) A 3(+1) + B5(+3) occurs a strong decrease of the lattice thermal conductivity. In the vicinity of x = 0. 50 the lattice part of thermal conductivity of (TlBiS2)1-x
(2PbS)x alloys decreases down to 0. 26 W/mK, i. e., it approaches the theoretical minimum. As a result, the thermoelectric figure of merit for these alloys ( 25%) exceeds the respective value for lead sulfide at room temperature. 相似文献
4.
Lü Qing WANG ShuFang LI LongJiang WANG JiangLong DAI ShouYu YU Wei FU GuangSheng 《中国科学:物理学 力学 天文学(英文版)》2014,57(9):1644-1648
High temperature electrical and thermal transport properties, that is, electrical conductivity, Seebeck coefficient and thermal conductivity, of CdO ceramics have been investigated. Because of the good electrical properties and low thermal conductivity, the dimensionless figure-of-merit ZT of the CdO ceramics reaches 0.34 at 1023 K. This value is comparable to the best reported ZT for the n-type oxide ceramic thermoelectric materials and remains as potential to be further improved by porosity controlling or nanostructuring. 相似文献
5.
利用包络函数的平面波展开法计算准二维纳米线阵列中的电子态,获得电输运系数表达式.同时,通过合理近似考虑边界散射对声子输运的影响,计算得到了晶格热导率.以Si/Ge体系为例,研究了纳米线阵列横向输运的热电特性.结果表明:结构优值与费米能级、纳米线直径及间距等参数相关.通过对结构参数的调整,纳米线阵列的横向输运可有效提高热电性能.
关键词:
热电性能
纳米线阵列
Seebeck系数
晶格热导率 相似文献
6.
纳米技术的快速发展使得对微纳尺度导热机理的深入研究变得至关重要. 理论和实验都表明, 在纳米尺度下声子热导率将表现出尺寸效应. 基于声子玻尔兹曼方程和修正声子平均自由程的方法得到了多约束纳米结构的声子热导率模型, 可以描述多个几何约束共同作用下热导率的尺寸效应. 不同几何约束对声子输运的限制作用可以分开计算, 总体影响则通过马西森定则进行耦合. 对于热流方向的约束, 采用扩散近似的方法求解声子玻尔兹曼方程; 对于侧面边界约束, 采用修正平均自由程的方法计算边界散射对热导率的影响. 得到的模型能够预测纳米薄膜(法向和面向)及有限长度方形纳米线的热导率随相应特征尺寸的变化. 与蒙特卡罗模拟及硅纳米结构热导率实验值的对比验证了模型的正确性. 相似文献
7.
Wenbing Du Yayun Gu Ke Wang Xinxin Yang Juanjuan Xing Kai Guo Jun Luo Jing-Tai Zhao 《Annalen der Physik》2020,532(11):1900390
Ge2Sb2Te5 is a famous phase-change memory material for rewriteable optical storage, which is widely applied in the information storage field. The stable trigonal phase of Ge2Sb2Te5 shows potential as a thermoelectric material as well, due to its tunable electrical transport properties and low lattice thermal conductivity. In this work, the carrier concentration and effective mass of Ge2Sb2Te5 are modulated by substituting Te with Se. Meanwhile, the thermal conductivity reduces from 2.48 W m−1 K−1 for Ge2Sb2Te5 to 1.37 W m−1 K−1 for Ge2Sb2Te3.5Se1.5 at 703 K. Therefore, the thermoelectric figure of merit zT increases from 0.24 for Ge2Sb2Te5 to 0.41 for Ge2Sb2Te3.5Se1.5 at 703 K. This study reveals that Se alloying is an effective way to enhance the thermoelectric properties of Ge2Sb2Te5. 相似文献
8.
利用水热法生成了形状规则、粒径均匀的球形ZnO纳米颗粒, 并超声分散于水中, 制备得到稳定的水基ZnO纳米流体. 实验测量水基ZnO纳米流体在体积分数和温度变化时的电导率, 并测试室温下水基ZnO纳米流体在不同体积分数下的热导率. 实验结果表明, ZnO纳米颗粒的添加较大地提高了基液(纯水)的热导率和电导率, 水基ZnO纳米流体的电导率随纳米颗粒体积分数增加呈非线性增加关系, 而电导率随温度变化呈现出拟线性关系; 纳米流体的热导率与纳米颗粒体积分数增加呈近似线性增加关系. 本文在经典Maxwell热导模型和布朗动力学理论的基础上, 同时考虑了吸附层、团聚体和布朗运动等因素对热导率的影响, 提出了热导率修正模型.将修正模型预测值与实验值对比, 结果表明修正模型可以较为准确地计算出纳米流体的热导率.
关键词:
水热法
电导率
热导率
热导模型 相似文献
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10.
Measurement of thermoelectric power Θ of pressed pellets of A-type Nd2O3 from 550 to 1180K and electrical conductivity (σ) at dc, 50 Hz, 1.542 kHz and 3 kHz at different temperatures is reported. It is concluded that electrical conduction at high
temperature (T>600K) in this solid is due to positive large polarons in O2− : 2p (valence) band and negative intermediate polarons in Nd3+ : 5d (conduction band). The energy band gap of the solid has been found to be 2.44 eV. At low temperatures, conduction by
hopping of charge carriers from one impurity centre to another has been predicted. 相似文献
11.
V. L. Gurevich V. I. Kozub A. L. Shelankov 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,51(2):285-292
We study thermoelectric effects in superconducting nanobridges and
demonstrate that the magnitude of these effects can be comparable or
even larger than that for a macroscopic circuit. It is shown that a
large gradient of the electron temperature can be realistically
created on a nanoscale and the masking effects due to spurious magnetic
fields can be minimised in nanostructures. For these reasons, nanodevices
can provide an interesting possibility to study the thermoelectric effect
in superconductors. 相似文献
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通过界面有效吸收系数的计算及界面对腔模的反射率的影响可知,采用双面键合技术制备面发射激光器应使键合界面处于驻波场分布零点位置,同时界面厚度应该小于20 nm以使器件光学性能受界面吸收系数的影响较小.采用有限元方法分析VCSEL温度分布,结果证实薄的键合界面使VCSEL有源区温度对界面的热导率和电导率改变不敏感,而厚的键合界面将可能使有源区温度有较大地升高,给器件带来严重的不良影响.亲水键合和疏水键合的SEM照片说明疏水处理界面较薄,适合用于器件的制备.而亲水处理界面厚度>40 nm,对器件的光、热特性不利
关键词:
键合
面发射激光器
热导率
电导率 相似文献
14.
WANG Zheng-Chuan SU Gang LI Ling GAO Jie 《理论物理通讯》2005,44(4):735-742
In order to consider the thermal and electrical coherent transport in a mesoscopic conductor under the influence of electron-electron interaction, in this paper, we establish a method in terms of which one can analytically obtain the Hartree self-consistent potential instead of computing it by the numerical iterative procedure as usual, which is convenient for us to describe the thermal and electric current flow through a mesoscopic conductor. If we study the electron-electron interaction at the Hartree approximation level, the Hartree potential satisfies the Poisson equation and Schroedinger equation, so when we expand the action function S(x) by Planck constant h, the self-consistent potential and the wavefunction can be solved analytically order by order, and the thermal and electrical conductance can thus be obtained readily. However, we just show the quantum corrections up to the second order. 相似文献
15.
We report on extensive experimental investigations of a single crystal of the orthorhombic uranium compound UCoGe. Bulk measurements on as-grown and annealed single crystals, recording magnetization, magnetic susceptibility, electrical resistivity, magnetoresistivity, thermopower, thermal conductivity and heat capacity data do not reproduce the previously reported coexistence of ferromagnetism with superconductivity. The latter phenomenon was only observed for the annealed sample at T SC = 0.65 K. New observations show a crossover at around 13 K, visible in thermal and transport measurements as well as the coherent state around 50 K, signaled by a wide knee in ρ(T). Above this temperature, UCoGe exhibits a single-ion Kondo-like effect. The magnetoresistivity of the annealed single crystal increases negatively down to 4.2 K, reaching as a large value about ?27% at a field of 8 T. The latter may be interpreted in terms of fairly strong magnetic fluctuations existing in UCoGe at low temperatures. 相似文献
16.
WANG Zheng-Chuan SU Gang LI Ling GAO Jie 《理论物理通讯》2005,44(10)
In order to consider the thermal and electrical coherent transport in a mesoscopic conductor under the influence of electron-electron interaction, in this paper, we establish a method in terms of which one can analytically obtain the Hartree self-consistent potential instead of computing it by the numerical iterative procedure as usual, which is convenient for us to describe the thermal and electric current flow through a mesoscopic conductor. If we study the electron-electron interaction at the Hartree approximation level, the Hartree potential satisfies the Poisson equation and Schrodinger equation, so when we expand the action function S(x) by Planck constant h, the self-consistent potential and the wavefunction can be solved analytically order by order, and the thermal and electrical conductance can thus be obtained readily. However, we just show the quantum corrections up to the second order. 相似文献
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Thermal properties of polypyrrole/polymethylmethacrylate (PPy/PMMA) composites were analyzed by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). A decrease in the glass transition temperatures with PPy concentration reveals the increase of segmental motion. The dielectric properties of these composites were studied for several weight concentrations of PPy in the frequency range between 500 Hz and 0.2 MHz, over the temperature range 23–110°C. Jonscher's phenomenological model has been used for modeling the dielectric response of the composite materials. This study shows that the results obtained for the dielectric response are in good agreement with the results of TGA and DSC measurements. 相似文献