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Gao Min 《Journal of Electronic Materials》2010,39(11):2459-2461
A frequently employed approach for determination of the maximum thermoelectric figure of merit of a material involves a calculation
of its maximum electrical power factor and the corresponding thermal conductivity. In this study, we show that the thermoelectric
figure of merit determined using this approach is likely to be limited by the Lorenz factor. The maximum thermoelectric figure
of merit is achieved at a different electrical conductivity. A simple way of estimating the optimal electrical conductivity
for obtaining the maximum thermoelectric figure of merit is presented. 相似文献
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一种测试半导体制冷器的瞬态方法 总被引:1,自引:0,他引:1
ZT值、最大制冷温差和响应时间是表征半导体制冷器性能的重要参数.文中介绍了一种能同时测量这三个参数的瞬态方法,并讨论了热沉对测试结果的影响.利用一个由恒流脉冲发生器和数据采集卡组成的简单测试系统测得制冷器在小电流下的电阻电压和塞贝克电压,通过这两个电压推导出ZT值、最大制冷温差.这种瞬态方法是非接触式测量,准确度高,可用于薄膜热电器件测试;另外瞬态方法耗时短,可大大缩短半导体制冷器可靠性测试的周期.采用这种方法对4mm×4mm×2.4mm的热电制冷器进行实验,环境温度300K时,测得ZT值为0.39,最大温差58.5K,响应时间20s. 相似文献
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Tomohiro Fujii Shinji Fukuda Masahiko Emoto Koudai Osada Toshio Kawahara Makoto Hamabe Hirofumi Watanabe Yury Ivanov Jian Sun Satarou Yamaguchi 《Journal of Electronic Materials》2011,40(5):691-695
Thermoelectric materials are promising candidates for use in energy-saving devices in many fields. They are also useful in
superconducting applications such as those using Peltier current leads (PCLs) to reduce system heat loss. In the case of PCLs,
consideration must be given to Joule heating. Furthermore, the performance of PCLs is intricately dependent on their thermoelectric
properties. In addition to the figure of merit Z, consideration of the electrical conductivity is also important for the design of high-performance PCLs. In this paper, we
discuss the resistivity dependence of the performance of PCLs using model parameters obtained from real devices. 相似文献
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ZT值、最大制冷温差和响应时间是表征半导体制冷器性能的重要参数.文中介绍了一种能同时测量这三个参数的瞬态方法,并讨论了热沉对测试结果的影响.利用一个由恒流脉冲发生器和数据采集卡组成的简单测试系统测得制冷器在小电流下的电阻电压和塞贝克电压,通过这两个电压推导出ZT值、最大制冷温差.这种瞬态方法是非接触式测量,准确度高,可用于薄膜热电器件测试;另外瞬态方法耗时短,可大大缩短半导体制冷器可靠性测试的周期.采用这种方法对4mm×4mm×2.4mm的热电制冷器进行实验,环境温度300K时,测得ZT值为0.39,最大温差58.5K,响应时间20s. 相似文献
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The effective properties of composites whose structure includes nanocontacts between bulk-phase macrocrystallites are considered.
A model for such a nanostructured composite is constructed. Effective values of the thermoelectric power, thermal and electrical
conductivities, and thermoelectric figure of merit are calculated in the mean-field approximation. 相似文献
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Tim C. Holgate YuFei Liu Dale Hitchcock Terry M. Tritt Jian He 《Journal of Electronic Materials》2013,42(7):1751-1755
Zirconium diselenide (ZrSe2) is one of many members of the layer-structured transition-metal dichalcogenide family. The structure of these materials features a weakly bonded van der Waals gap between covalently bonded CdI2-type atomic layers that may host a wide range of intercalants. Intercalation can profoundly affect the structural, thermal, and electronic properties of such materials. While the thermoelectric potential of layer-structured transition-metal dichalcogenides has been formerly studied by several groups, to our best knowledge, neither the thermoelectric properties of ZrSe2 nor the impact of intercalation on its thermoelectric properties have been reported (specifically, the full evaluation of the dimensionless figure of merit, ZT, which includes the thermal conductivity). In this proof-of-principle study, ZrSe2 single crystals have been synthesized using an iodine-assisted vapor transport method, followed by a wet-chemistry lithium intercalation process. The results of resistivity, thermopower, and thermal conductivity measurements between 10 K and 300 K show that Li intercalation induced additional charge carriers and structural disorder that favorably affected the thermoelectric properties of the material. As a result, a dimensionless figure of merit ZT ≈ 0.26 has been attained at room temperature in a Li-intercalated sample, representing nearly a factor of three improvement compared with the pristine sample. These improvements, along with the abundance, relatively low toxicity, and low cost of such materials, merit further thermoelectric investigations of intercalated zirconium diselenide, especially in conjunction with a substitutional doping approach. 相似文献
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The thermoelectric figure of merit of structures with multiple quantum wells (MQWs) was calculated taking into account the variations in the relaxation time of charge carriers compared to that in a bulk sample. The mechanisms of scattering by acoustic phonons, at the short-range impurity potential, and the polar scattering in the approximation of the isotropic parabolic dispersion law of the charge carriers were taken into account. The model used is based on the assumption that the phonon spectrum in the MQW structures is no different from the spectrum of the bulk crystal. In addition, the scattering is assumed to be elastic and the relaxation-time approximation was used for all three mechanisms of scattering. A comparison with the results of calculations for a bulk sample shows that the expression for thermoelectric figure of merit is exactly the same for a MQW structure as for a bulk sample if the decrease in the charge-carrier relaxation time in MQW structures is taken into account. The magnitude of the figure of merit for a MQW structure is found to be equal to that for a bulk sample if the chemical potential in each of the cases is chosen from the condition for the highest figure of merit. 相似文献
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Isachenko G. N. Samunin A. Yu. Konstantinov P. P. Kasyanov A. A. Masalimov A. 《Semiconductors》2019,53(5):607-610
Semiconductors - High values of the thermoelectric figure of merit (ZT = 1.5) in Mg2Si–Mg2Sn solid solutions are caused by a low thermal conductivity and a complex band structure, which is... 相似文献
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The thermoelectric figure of merit of a semiconductor p-n junction is calculated in terms of the diode theory taking account of the bipolar thermal conductivity. The thermoelectric figure of merit of a Bi2Te3 diode is estimated and it is shown that the Ioffe criterion may be at the same level as the best modern thermoelectric materials but cannot exceed unity. 相似文献
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The relation between the thermoelectric figure of merit Z and the basic properties of the material such as carrier mobilities, band structure, thermal conductivity and minority carrier lifetime is discussed. For isotropic materials with parabolic bands it is shown that the figure of merit based on the Seebeck coefficient will increase when a magnetic field is applied, if acoustic-mode scattering is predominant. If optical-mode scattering is predominant, the figure of merit will increase if ZT>0.77. Materials for devices based upon the Nernst or Ettingshausen effects will have large figures of merit only if 1) (m*)3/2µ/κL is large, 2) the energy gap is less than kT, and 3) the electron and hole mobilities are similar. Materials requirements for Nernst- and Seebeck-type devices are compared. 相似文献
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Semiconductors - The broad application of thermoelectricity is constrained by the low efficiency of thermoelectric elements, which is mainly determined by the thermoelectric figure of merit of... 相似文献
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M. T. Barako W. Park A. M. Marconnet M. Asheghi K. E. Goodson 《Journal of Electronic Materials》2013,42(3):372-381
Thermoelectric modules experience performance reduction and mechanical failure due to thermomechanical stresses induced by thermal cycling. The present study subjects a thermoelectric module to thermal cycling and evaluates the evolution of its thermoelectric performance through measurements of the thermoelectric figure of merit, ZT, and its individual components. The Seebeck coefficient and thermal conductivity are measured using steady-state infrared microscopy, and the electrical conductivity and ZT are evaluated using the Harman technique. These properties are tracked over many cycles until device failure after 45,000 thermal cycles. The mechanical failure of the TE module is analyzed using high-resolution infrared microscopy and scanning electron microscopy. A reduction in electrical conductivity is the primary mechanism of performance reduction and is likely associated with defects observed during cycling. The effective figure of merit is reduced by 20% through 40,000 cycles and drops by 97% at 45,000 cycles. These results quantify the effect of thermal cycling on a commercial TE module and provide insight into the packaging of a complete TE module for reliable operation. 相似文献
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The increase in the thermoelectric figure of merit in layered structures with quantum wells is calculated for the case of polar charge-carrier scattering by optical phonons. On the basis of previous and new calculations, it is concluded that the quantum confinement effect can give rise to the increase in the figure of merit only if the probability of carrier scattering decreases with increasing wave vector transfer. 相似文献
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In the present study we explore the structural, electronic and thermoelectric properties of IV-VI semiconductors using first principle calculations based on the density functional theory. Generalized gradient approximation (GGA-PBEsol) is used as an exchange-correlation functional for the structural properties of the different crystal phases of these semiconductors. The compounds SnS, SnSe, GeS and GeSe favor orthorhombic structure, lead chalcogenides (PbS, PbSe and PbTe) are stable in the cubic rocksalt structure, while SnS2 and SnSe2 exist in hexagonal structure. For band structures additional to GGA, modified Becke and Johnson (mBJ) exchange potential is used. These compounds are narrow band gap semiconductors in the energy range 0.2–2.8 eV. These binary IV-VI chalcogenides have direct band gap nature in cubic crystals while indirect in the orthorhombic phases. The post-DFT (BoltzTraP) calculations are performed to estimate Seebeck coefficient, electric and thermal conductivities, power factor and figure of merit of these compounds to check their applicability in thermoelectric devices. Spin orbit coupling effect influences the electronic and thermoelectric properties of these compounds due to the large size of the constituent elements. Further, the total thermal conductivity is computed using ad-hoc calculation with the experimental results. The calculated values of figure of merit for PbS, PbSe, PbTe and SnTe are in the range 0.68–0.77 at room temperature. 相似文献
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Andrea De Marchi Valter Giaretto Simone Caron Andrea Tona 《Journal of Electronic Materials》2013,42(7):2067-2072
Measurements of the dimensionless figure of merit of different thermoelectric devices are presented and discussed, as obtained with a prototype zT meter which is based on the porcupine method. The instrument’s architecture and operation are discussed to support claims made on the accuracy of results. Different types of thermoelectric devices were tested, focusing on the size of the porcupine’s snout for each. The latter is probably the major source of uncertainty in Harman methods, but is well measurable with the porcupine method, which therefore allows definition of the correction needed to obtain accurate evaluation of zT. Accuracies much better than 1% in the determination of the dimensionless figure of merit and series resistance are possible in this way. A survey of various devices is reported, and results are shown to indicate that corrections up to the 10% level and more are needed, depending on the configuration. 相似文献