Effects of AI Addition on the Thermoelectric Properties of Zn-Sb Based Alloys

The β-Zn4Sb3, emerged as a compelling p-type thermoelectric material, is widely used in heat-electricity conversion in the 400-650 K range. In order to probe the effects of slight doping on the crystal structure and physical properties, we prepared the samples of Al-added Zn-Sb based alloys by spark plasma sintering and evaluated their microstructures and thermoelectric properties. After a limited Al addition into the Zn-Sb based alloys we observed many phases in the alloys, which include a major phase β-Zn4Sb3,intermetallic phases ZnSb and AISb. The major β-Zn4Sb3 phase plays a fundamental role in controlling the thermoelectric performance, the precipitated phases ZnSb and AISb are of great importance to tailor the transport properties, such as the gradual enhancement of lattice thermal conductivity, in spite of an increased phonon scattering in additional grain boundaries. The highest thermoelectric figure of merit of 0.55 is obtained for the alloy with a limited AI addition at 653 K, which is 0.08 higher than that of un-doped β-Zn4Sb3 at the corresponding temperature. Physical property experiments indicate that there is a potentiality for the improvement of thermoelectric properties if a proper elemental doping is carried out into the Zn-Sb based alloys, which was confirmed by AI addition in the present work.     

热压法制备P型Si0.8Ge0.2合金及其热电性能

采用真空熔炼和热压烧结法制备了B含量为0．3％～０．72％的P型Si0．8Ge0．2固溶体合金，对样品进行了物相结构分析和微观形貌表征，并研究了掺B量对合金热电性能的影响。结果表明：随着B掺杂量的增加，电导率σ增大，塞贝克系数α减小。功率因子α2σ在B掺入量约为0．6％时达到最大值。     

High temperature Seebeck coefficient and resistance measurement system for thermoelectric materials in the thin disk geometry

A versatile apparatus to measure the cross-plane Seebeck coefficient and the resistivity of bulk samples shaped as disks or thin plates, over a temperature range of 300 K-620 K with possible extension to higher temperatures, is presented. It is constructed from readily available equipment and instrumentation with parts that are easily manufactured. The Seebeck coefficient is measured over an average region of the sample under steady-state conditions. The sample resistance is measured using a four-point alternating current method and scaled to room temperature measurements with known geometry to calculate resistivity. A variety of sample shapes are supported. Most importantly, the support of the thin disk geometry allows for the very same samples to be used in a laser flash instrument. The design allows for rough vacuum, high vacuum, or purging with inert gases in the sample chamber. Measurements on thermoelectric ZnSb and a Ni reference material are presented.     

Rapid consolidation of powdered materials by induction hot pressing

A rapid hot press system in which the heat is supplied by RF induction to rapidly consolidate thermoelectric materials is described. Use of RF induction heating enables rapid heating and consolidation of powdered materials over a wide temperature range. Such rapid consolidation in nanomaterials is typically performed by spark plasma sintering (SPS) which can be much more expensive. Details of the system design, instrumentation, and performance using a thermoelectric material as an example are reported. The Seebeck coefficient, electrical resistivity, and thermal diffusivity of thermoelectric PbTe material pressed at an optimized temperature and time in this system are shown to agree with material consolidated under typical consolidation parameters.     

High temperature Z-meter setup for characterizing thermoelectric material under large temperature gradient

To properly estimate a thermoelectric material's performance, one should be able to characterize a single thermoelectric (TE) element with a large temperature gradient. In this work, we present an experimental setup including a Z-meter that can heat the sample to a very high temperature of 1200 °C in vacuum. The Z-meter can simultaneously measure all three thermoelectric parameters (Seebeck coefficient, thermal conductivity, and electrical conductivity), as well as measure the generated power and the efficiency for a single TE leg. Furthermore, this measurement of power conversion efficiency is used to generate a measure of the material's ZT. An in situ metallurgical bond was used to achieve low thermal (0.05 Kcm(2)∕W) and electrical (3 mΩ) contact parasitics. An integrated strain gauge ensures reproducible thermal contact. At high temperature (>600 K), radiative heat transfer is modeled and the instrument is optimized to suppress the systematic error to below 7%. The TE parameters and ZT for a bulk-sample (Bi(2)Te(3)) and a thin-film sample (ErAs:InGaAlAs) with a large temperature gradient (ΔT ～ 200 K) have been measured and are within 3%-7% of the independently measured values.     

热压法制备N型Si0.8Ge0.2合金及其热电性能

采用真空熔炼和热压烧结法制备了掺P量为0．1％～0．3％的N型Si0．8Ge0．2固溶体合金，对样品进行了物相结构分析和微观形貌表征，并研究了掺P量对合金室温热电性能的影响。结果表明：随着P掺杂量的增加，电导率σ增加缓慢，各样品相差不大，塞贝克系数α明显减小。功率因子α2σ随之减小。     

Simple apparatus for the multipurpose measurements of different thermoelectric parameters

A simple apparatus for the simultaneous measurement of Seebeck coefficient (α) and electrical resistivity (ρ) in the temperature range 100-600 K, Hall coefficient (R_H) and transverse Nernst-Ettingshausen coefficient (N) in the temperature range 300-600 K of the bar shaped samples has been fabricated. The instrument has been designed so simply that the sample can be easily mounted for the fast measurements of different thermoelectric parameters. The sample holder assembly of the apparatus has been designed so cleverly that any part of that section can be replaced in case of any damage; and so it can be regarded as a modular based system. The apparatus is relatively cheaper in cost and also portable.     

汽车尾气温差发电装置中热电器件的试验研究

为了利用热电器件回收汽车尾气的废热进行发电,构建了一个可模拟汽车尾气温差发电装置的热电器件测试平台,测试了不同热源温度、冷源温度、安装压力以及相同冷热源温差而不同冷热源温度下国产某型Bi2Te3基低温热电器件的输出性能。结果表明,单个热电器件的输出性能与其安装压力和冷热源温差成正比,在相同冷热源温差条件下可适当降低冷源温度以提高其性能;随着冷热源温差增大,热电器件的最大功率所对应的输出电流明显增大;利用汽车发动机自身冷却系统中约90℃的冷却水对汽车尾气温差发电装置进行冷却时,当热端温度达到350℃的最大耐温值,安装压力大于57kPa时,单个热电器件的最大输出功率在3W以上。最后,基于该热电器件提出了汽车尾气温差发电装置的优化设计策略及其工作条件。     

汽车尾气热电转换装置电气拓扑结构优化

针对汽车尾气热电转换装置多个热电器件温差和自身特性的差异,为了最大化发挥各热电器件的发电潜能,对热电转换装置的热电模块进行拓扑结构的优化,基于图论的方法将热电模块的串并联问题抽象为数学问题,再针对性地设计了算法,通过实验室台架实验测试和数据验证,使得热电转换装置对外输出最大功率。     

轧制与热处理工艺在Bi系超导材料制备中的作用

利用轧制与热处理工艺对液氮温区不超导的Ｂｉ系烧结块材进行加工处理,使度样获得了超导电性,且热处理工艺的稳定性、重复性较好。Ｘ射线衍射分析及高温超导相组成分析表明,超导晶粒沿轧制平面的取向分布以及１１０Ｋ相含量的提高是试样超导性改善的主要原因。     

Study of Electrical Resistivity of Powder Materials Obtained by Oxidation of Hard Alloys

An electrical resistivity of oxide powder materials obtained by high-temperature heating of hard-alloy tool materials has been measured. The resistivity of oxide powder increases with increasing cobalt content in raw hard alloys as well as the oxidation temperature. On the contrary, the increase of concentration of titanium and tantalum carbides is accompanied by the resistivity reduction. The increase of pressure on the powder also results in the resistivity decrease. There exists a correlation between the wear resistance of cutting tools and pressure dependence of the resistivity of oxide powders. Therefore the measurement of the resistivity of oxide powders can be successfully applied for the quality estimation and forecasting of the service properties of hard-alloy production.     

基于温差发电的自动搅拌马克杯设计与实现

针对当前市场上销售的普通马克杯功能单一,带有电动搅拌功能的马克杯搅拌不均匀,能源损耗的情况,设计了一种基于温差发电的自动搅拌马克杯。采用温差发电作为供电来源,实现全自动搅拌,杯内温度可实时监测。设置杯内饮料的保温温度,具有操作人性化,界面友好,能源合理应用的特点。     

汽车尾气温差发电系统车载兼容性多目标优化研究

汽车尾气温差发电系统在接入发动机的排气管时会改变其气流,为了尽可能降低对发动机原有性能的影响,提高汽车尾气温差发电系统的发电性能,针对汽车尾气温差发电用六边形热交换器,以表面平均温度最高和压力损失最小为目标进行其车载兼容性优化。基于CFD软件搭建了热交换器的有限元仿真模型,研究热交换器的入口气体流速对其表面温度和压力损失的影响,以及入口气体温度对其表面温度的影响,以翅片长度、角度、宽度及翅片间的间距为设计变量,针对试验数据建立高斯过程回归代理模型,并采用灰狼算法在多目标优化函数空间中寻求最优解。结果表明,与经典的NSGA-Ⅱ算法相比,利用多目标灰狼算法进行优化时所得Pareto解集更为集中,设定的评价指标值也更高;与优化前的几种结构相比,优化后的热交换器表面平均温度有所降低,但压力损失下降显著;与空腔结构热交换器相比,其表面平均温度和压力损失均有提升,压力损失增加幅值在可接受范围内,证明优化后的热交换器能有效兼顾汽车尾气温差发电系统的功率及其车载兼容性。     

集装箱船余热回收系统中温差发电模块的热电耦合分析

随着热电发电、热电制冷技术研究的不断深入,热电在船舶余热回收方面有了重大突破.以集装箱船余热回收系统中温差发电模块为研究对象,考虑了热电模块热端和冷端温度差存在温度变化的实际情况,运用ANSYS软件建立了热电单P-N结模型,分析了热电单元温度场的分布规律,得到了温差发电系统的输出特性,根据分析结果进行了温差发电模块用于...     

Thermal property of insulating material at cryogenic temperature

The thermal property of insulation material is essential in developing high temperature superconductor (HTS) devices operating at around liquid nitrogen temperature. Unlike metallic materials, nonmetallic materials have a thermal resistance; therefore, accurate estimate of the heat flow is difficult in the case of nonmetallic materials. In this study, a precise instrument is developed for measuring the thermal property of insulating materials over a temperature range of 30 K to approximately the room temperature by using a cryocooler. The cold head of the cryocooler is thermally anchored to the thermal link and used to cool the apparatus to a desired temperature. The temperature distribution in specimen is measured with respect to the supplied heating power, from which the thermal conductivity is calculated and compared with published data for accuracy confirmation. The effective thermal conductivity of polypropylene laminated paper (PPLP) is presented and the trend in the behavior of conductivity near liquid nitrogen temperature is also discussed.     

Simple uniaxial pressure device for ac-susceptibility measurements suitable for closed cycle refrigerator system

A simple design of the uniaxial pressure device for the measurement of ac-susceptibility at low temperatures using closed cycle refrigerator system is presented for the first time. This device consists of disc micrometer, spring holder attachment, uniaxial pressure cell, and the ac-susceptibility coil wound on stycast bobbin. It can work under pressure till 0.5 GPa and at the temperature range of 30-300 K. The performance of the system at ambient pressure is tested and calibrated with standard paramagnetic salts [Gd(2)O(3), Er(2)O(3), and Fe(NH(4)SO(4))(2)6H(2)O], Fe(3)O(4), Gd metal, Dy metal, superconductor (YBa(2)Cu(3)O(7)), manganite (La(1.85)Ba(0.15)MnO(3)), and spin glass material (Pr(0.8)Sr(0.2)MnO(3)). The performance of the uniaxial pressure device is demonstrated by investigating the uniaxial pressure dependence of La(1.85)Ba(0.15)MnO(3) single crystal with P||c axis. The Curie temperature (T(c)) decreases as a function of pressure with P||c axis (dT(c)dP(||c axis)=-11.65 KGPa) up to 46 MPa. The design is simple, is user friendly, and does not require pressure calibration. Measurement can even be made on thin and small size oriented crystals. The failure of the coil is remote under uniaxial pressure. The present setup can be used as a multipurpose uniaxial pressure device for the measurement of Hall effect and thermoelectric power with a small modification in the pressure cell.     

A Cell for Thermoelectric and Contact Phenomena Investigations

A cell for obtaining a large temperature gradient (up to 70 K/mm) along a sample for thermoelectric and contact phenomena investigations of a wide class of dielectric and semiconductor materials in a temperature range from 300 to 1000 K is described.     

Comment on "A versatile thermoelectric temperature controller with 10 mK reproducibility and 100 mK absolute accuracy" [Rev. Sci. Instrum. 80, 126107 (2009)

Libbrecht and Libbrecht recently described a thermoelectric temperature controller for which they claimed an absolute accuracy of 100 mK. They did not specify the heat-dissipation coefficient for their thermistor temperature sensor-which would dissipate more power than is usual in such circuits- nor make any allowance for self-heating in the thermistor. Self-heating can be expected to have introduced more than 100 mK of absolute error in their circuit.     

塑料微流控芯片热压成形温度控制装置

采用聚合物如塑料等制作微流控芯片是拓展芯片应用,实现芯片产业化的关键。温度是塑料微流控芯片热压成形过程中的重要工艺参数。本文采用半导体热电致冷堆,设计了适合塑料芯片制作的温度控制装置;分析了升降温过程中所需的加热／制冷功率,并对升降温特性进行了研究;设计了半导体热电致冷堆供电电源装置。对温度控制装置的升／降温及温度控制精度进行了实验,并给出了实验结果。     

用于热机械微纳加工的掺Al多晶硅加热器

针对热机械式微纳米结构的加工,提出了一种以掺Al多晶硅为材料,集成于微悬臂梁上的加热器.采用Al诱导退火晶化(AIC)方法,在750 K对Al/a-Si∶H复合薄膜低温晶化18 h,制备出掺Al多晶硅.通过低温退火,使复合薄膜的拉曼特征峰由478 cm-1移至520 cm-1,完成由非晶硅向多晶硅的转变;由四探针仪测得...