热电材料塞贝克系数测试影响因素研究

为提高热电材料塞贝克系数的测试准确度,以康铜合金、钴酸钙、碲化铅、氧化锌等典型块体热电材料为测试对象进行一系列测试,研究测温热电偶的塞贝克效应、温差设置、数据处理方式对塞贝克系数测试的影响。结果表明:热电偶的塞贝克效应对Seebeck系数测试准确度的影响是显著的;样品两端温差设置在5~20℃之间,直线拟合方式采用不过原点拟合,可以使Seebeck系数测试结果的准确度得到大幅提高。     

不同环境下烧结的Ca3Co4O9的热电性能

采用传统的固相反应法在不同的氧压下烧结制得Ca3Co4O9样品,并对其进行了结构和热电性能表征.经研究发现,在氧气环境下烧结样品可以抑制Ca3Co4O9在高温下分解,提高其烧结温度.在氧气环境中烧结的样品成相优于在空气中烧结的样品.一定氧压下烧结样品的电阻率比常压下烧结样品的电阻率大,但是Seebeck系数明显提高,因而改善了Ca3Co4O9的热电性能.     

高压制备AgSbTe_2的微结构及高温电学性能研究

采用高压合成技术,制备出了热电材料AgSbTe2,并且研究了AgSbTe2样品微结构和高温电学输运性质。X射线衍射测试结果表明,高压合成的AgSbTe2样品中含有微量的Sb2Te3,电子能谱测试结果表明Ag、Sb、Te 3种元素分布很均匀。电学性能测试表明,在高压的作用下,AgSbTe2样品的载流子浓度增大;随着测试温度的升高,电导率降低,Seebeck系数增大。4 GPa高压合成的AgSbTe2样品在573 K温度下具有最高的功率因子(约18.1μW/(cm·K2))。     

热电材料塞贝克系数测试影响因素的研究

为提高热电材料塞贝克系数的测试准确度,主要以康铜合金和钴酸钙为测试对象进行了一系列测试,其中以典型的碲化铋、方钴矿、硒化铅块体热电材料为辅助研究对象,具体研究测温热电偶的塞贝克效应、温差设置、数据处理方式对塞贝克系数测试结果的影响。结果表明:热电偶的塞贝克效应对Seebeck系数测试准确度的影响是显著的;样品两端温差设为10K以上,多组温差间的梯度设为3K以上,直线拟合方式采用不过原点拟合,可以使Seebeck系数测试结果的准确度得到很大提高。     

不同质子酸掺杂聚苯胺的热电性能

采用化学氧化聚合法分别在高氯酸、硫酸、对甲基苯磺酸、樟脑磺酸溶液中合成了掺杂态聚苯胺,并研究了其热电性能。随着温度的升高,所有样品的电导率降低,Seebeck系数与ZT值均增加。对甲基苯磺酸掺杂的聚苯胺的电导率最高,303K时达811.1S/m,但其Seebeck系数在高温下增加缓慢。在373K以下,对甲基苯磺酸掺杂样品的ZT值最高;在373K以上,高氯酸掺杂样品的热电性能最好,在423K时ZT值达3.18×10-4。     

NiO基氧化物热电材料的合成及其性能

采用溶胶凝胶法制备了Li掺杂的NiO基氧化物热电材料,研究了Li掺杂对其热电性能的影响,实验结果表明:在x=0.03,0.06,0.09掺杂比例范围,Li+很好地进入了NiO的晶格,没有形成新的杂相。热电性能测试结果显示,在室温至750K的范围内随着Li掺杂量的增加,电导率显著增加,而样品的Seebeck系数随着掺杂浓度增高明显降低,样品Ni0.94Li0.06O在750K的功率因子PF=1.9×10-5 W.m-1.K-2,随温度升高,PF增加趋势明显,表明在高温环境中可具有更大的PF。     

高压合成纳米晶Bi0.85Sb0.15的低温热电性

通过机械合金化法获得Bi0.85Sb0.15纳米晶粉末材料,在常温下冷压成型并分别在不同温度下进行高压处理,制备出块状样品.X-ray衍射实验证实已形成了Bi0.85Sb0.15单相合金.测量了样品在80～300 K温区的Seebeck系数和电导率,计算出材料的功率因子与温度的关系.在523 K 6 GPa下压制30 min的样品,其Seebeck系数在150 K达到-173μV/K,比同温度下单晶材料样品的Seebeck高大约60%,功率因子在200 K达到3.27×10-3 W/m·K2,表明高压处理可以有效改善材料热电性能.高分辨电镜分析发现材料中存在均匀分布的小于5 nm的"纳米点","纳米点"的存在导致材料Seebeck系数在低温显著提高.     

高压合成纳米晶Bi0．85Sb0．15的低温热电性能

通过机械合金化法获得Bi0．85Sb0．15纳米晶粉末材料,在常温下冷压成型并分别在不同温度下进行高压处理,制备出块状样品．X-ray衍射实验证实已形成了Bi0.85Sb0．15单相合金．测量了样品在80～300 K温区的Seebeck系数和电导率,计算出材料的功率因子与温度的关系．在523 K 6 GPa下压制30 min的样品,其Seebeck系数在150 K达到-173μV／K,比同温度下单晶材料样品的Seebeck高大约60％,功率因子在200 K达到3．27×10^-3W／m·K2,表明高压处理可以有效改善材料热电性能．高分辨电镜分析发现材料中存在均匀分布的小于5 nm的“纳米点”,“纳米点”的存在导致材料Seebeck系数在低温显著提高．     

溅射沉积掺Ag的SnSe薄膜的微结构和热电性能

使用粉末烧结SnSe合金靶高真空磁控溅射制备掺杂Ag的SnSe热电薄膜,利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和能谱仪(EDS)等手段分析薄膜的相组成、表面形貌、截面形貌、微区元素含量和元素分布,利用塞贝克系数/电阻分析系统LSR-3测量沉积薄膜的电阻率和Seebeck系数,研究了不同Ag含量SnSe薄膜的热电性能。结果表明,采用溅射技术可制备出正交晶系Pnma结构的SnSe相薄膜,掺杂的Ag在薄膜中生成了纳米Ag₃Sn。与未掺杂Ag相比,掺杂Ag的SnSe薄膜其电阻率和Seebeck系数(绝对值,下同)明显减小。并且在一定掺杂范围内,掺杂Ag越多的薄膜电阻率和Seebeck系数越小。未掺杂Ag的SnSe薄膜样品,其Seebeck系数较大但是电阻率也大,因此功率因子较小。Ag掺杂量(原子分数)为7.97%的样品,因其Seebeck系数绝对值较大而电阻率适当,280℃时的功率因子最大(约为0.93 mW·m^-1·K^-2),比未掺杂Ag的样品(PF=0.61 mW·m^-1·K^-2)高52%。掺杂适量的Ag能提高溅射沉积的SnSe薄膜的热电性能(功率因子)。     

小试样高通量蠕变及蠕变裂纹扩展试验装置设计

对于某些取样受限的结构,如在役构件、薄壁件、焊接接头、功能性梯度结构,无法采用传统试样测试获得高温蠕变及裂纹扩展性能,小试样测试方法使得此类构件的高温力学性能的获取成为可能。但现有小试样蠕变试验装置用途单一且存在试样氧化的问题,无法满足试验要求。本文设计一种基于小试样的材料蠕变及蠕变裂纹扩展性能测试装置,装置配备专用夹具和真空系统,可满足不同种类小试样真空环境下的高温试验,避免试样氧化,并可同时完成6个同类或不同类型小试样的蠕变和蠕变裂纹扩展试验。装置采用马弗炉对试样加热,最高试验温度可达1 200℃。采用光栅位移传感器测量小试样变形量,直流电位法测量裂纹长度,提高了变形测量精度。试验结果表明,该装置可以精确测量小试样位移和裂纹长度,用以研究材料蠕变及裂纹扩展性能。     

热电材料塞贝克系数的不确定度评定

热电材料是一类可以将热能和电能直接相互转化的新型功能材料。塞贝克系数作为评价热电材料性能的重要参数,其准确测量尤为关键。基于准确测量方法,建立了塞贝克系数的溯源路径,研究了塞贝克系数测量仪器的溯源性,验证了测量方法的准确性,以P型碲化铋Bi2Te3块体热电材料作为测量对象进行了测量不确定度评定,其相对扩展不确定度为0.46%～2.52%(k=2)。     

聚噻吩及其衍生物热电材料研究进展

近来,聚合物热电材料因其成本低、资源丰富、热导率低等优势被认为是最有前途的热电材料之一。聚噻吩及其衍生物是研究较为广泛的一类聚合物热电材料。综述了近年来聚噻吩、聚噻吩衍生物以及聚噻吩基/无机复合热电材料在热电领域的研究进展。已有研究表明,聚噻吩及其衍生物热电材料具有高的Seebeck系数,其See-beck系数与电导率通常是此消彼长的关系。通过制备低维材料,与高电导率的无机纳米材料复合以及适度掺杂等方法可有效提高聚噻吩及其衍生物的热电性能。     

Zn-Sb双掺杂Mg2(Si,Sn)合金的热电性能

Mg₂(Si,Sn)合金热电材料具有成本低廉、环境友好等优点, 作为一种绿色环保的中温区热电材料一直受到广泛关注。在Mg₂(Si,Sn)基材料中掺杂大剂量Sb可诱发Mg空位, 从而有效降低材料的热导率, 但同时Seebeck系数也会降低。研究采用高温熔炼及真空热压法成功合成了Mg_2.12-ySi_0.4Sn_0.5Sb_0.1Zn_y (y=0~0.025)试样, 通过在大剂量Sb掺杂的Mg₂(Si,Sn)基材料中添加Zn元素, 研究了大剂量Sb和微量Zn双掺杂对材料电声输运特性的综合影响。研究结果表明, Zn-Sb双掺杂可通过有效抑制材料电子热导率的方法大幅降低Mg₂(Si,Sn)合金材料的总热导率, 与此同时明显提高掺Zn试样的塞贝克系数以弥补其电导率的损失, 维持材料较为优异的电学性能。最终, 热导率的大幅优化及电学性能的维持实现了材料综合热电性能的显著提升, 其中, 成分为Mg_2.095Si_0.4Sn_0.5Sb_0.1Zn_0.025的材料在823 K下热电优值ZT达到1.42。     

A Mechanism for the Oxidation-Related Influence on the Thermoelectric Behavior of Palladium

Oxidation of thermocouple elements can degrade the accuracy of thermocouple-based temperature measurements. As a particular example of such effects, oxidation of the Pd element of a platinum/palladium thermocouple is known to increase the thermoelectric emf by an amount equivalent to a temperature change of the order of 100 mK to 200 mK at 420 °C (G. W. Burns, D. C. Ripple, Proceedings of TEMPMEKO ‘96, 6th International Symposium on Temperature and Thermal Measurements in Industry and Science. Levrotto and Bella, Torino, 1997, 171–176). A possible physical mechanism to explain how oxidation affects the thermoelectric output of a Pt/Pd thermocouple is proposed. The analysis hinges on the hypothesis that the oxide-induced strain within the Pd thermoelement leads to a change in the Seebeck coefficient, and therefore to the thermoelectric emf. A theoretical model relating deformation of the palladium lattice to the change in the Seebeck coefficient is presented. The level of agreement between the calculation and the experimental observations suggests that oxide-induced strain in the Pd thermoelement is a likely explanation for the change in thermoelectric output of a Pt/Pd thermocouple within the temperature range where oxidation is active.     

Traceable Thermoelectric Measurements of Seebeck Coefficients in the Temperature Range from 300 K to 900 K

This work is focused on the characterization of thermoelectric reference materials with traceable Seebeck coefficients in the temperature range from 300 K to 900 K. The presented measurement system will provide a relative uncertainty of the measurement of the Seebeck coefficient of about 5 %. The Seebeck coefficient represents an important component of the figure of merit ZT and thus the low uncertainty of the Seebeck coefficient will also lower the uncertainty of the ZT value. We also present data which lead to the launch of the certification process of a NiCu-alloy according to the ISO Guide 35.     

High Thermoelectric Performance in n-Type Perylene Bisimide Induced by the Soret Effect

Low-cost, non-toxic, abundant organic thermoelectric materials are currently under investigation for use as potential alternatives for the production of electricity from waste heat. While organic conductors reach electrical conductivities as high as their inorganic counterparts, they suffer from an overall low thermoelectric figure of merit (ZT) due to their small Seebeck coefficient. Moreover, the lack of efficient n-type organic materials still represents a major challenge when trying to fabricate efficient organic thermoelectric modules. Here, a novel strategy is proposed both to increase the Seebeck coefficient and achieve the highest thermoelectric efficiency for n-type organic thermoelectrics to date. An organic mixed ion–electron n-type conductor based on highly crystalline and reduced perylene bisimide is developed. Quasi-frozen ionic carriers yield a large ionic Seebeck coefficient of −3021 μV K⁻¹, while the electronic carriers dominate the electrical conductivity which is as high as 0.18 S cm⁻¹ at 60% relative humidity. The overall power factor is remarkably high (165 μW m⁻¹ K⁻²), with a ZT = 0.23 at room temperature. The resulting single leg thermoelectric generators display a high quasi-constant power output. This work paves the way for the design and development of efficient organic thermoelectrics by the rational control of the mobility of the electronic and ionic carriers.     

The thermoelectric properties of Co4Sb12-xTex synthesized at different pressure

Skutterudite compounds Co₄Sb_12-xTe_x (0.1 ≤ ×≤0.8) was synthesized successfully by high temperature and high pressure (HTHP) method and characterized with X-ray diffractometry and thermoelectric properties measurements. The samples prepared by HTHP are nearly with the single phase CoSb₃. The electrical resistivity, Seebeck coefficient and thermal conductivity were all depending on synthetic pressure and the Te content of the Skutterudite compounds were performed at room temperature. As our expected, the Seebeck coefficient increased with an increase of the synthetic pressure and the thermal conductivity decreased with an increase of the synthetic pressure. These results indicated that HTHP technique may be helpful to prepare thermoelectric materials with enhanced thermoelectric properties.     

A nanoscale standard for the Seebeck coefficient

The Seebeck coefficient, a key parameter describing a material's thermoelectric performance, is generally difficult to measure, and no intrinsic calibration standard exists. Quantum dots and single electron tunneling devices with sharp transmission resonances spaced by many kT have a material-independent Seebeck coefficient that depends only on the electronic charge and the average device temperature T. Here we propose the use of a quantum dot to create an intrinsic, nanoscale standard for the Seebeck coefficient and discuss its implementation.     

聚(3,4-二氧乙撑噻吩)的制备及其热电性能研究

聚(3,4-二氧乙撑噻吩)(PEDOT)以其独特的热稳定性和较高的电导率而引起了广泛关注.首次系统研究了导电PEDOT的热电性能,主要包括电导率、Seebeck系数和热导率,详细比较了化学和电化学方法制备的PEDOT样品在热电性能上的差异.结果表明PEDOT的热电优值最大可以达到1.87×10~(-3)(T=270K),且在相同条件下,PEDOT的热电性能要高出其它有机高分子材料大概一个数量级,而且PEDOT的热电性能依然存在较大的提高潜力.     

Traceable Measurements of Seebeck Coefficients of Thermoelectric Materials by Using Noble Metal Thermocouples

The characterization of thermoelectric materials as reference materials for Seebeck coefficients at the Physikalisch-Technische Bundesanstalt (PTB) is based on the usage of gold/platinum differential thermocouples. In the case of thermoelectric materials containing silicon, the gold/platinum thermocouples are insufficient due to reactions with the silicon when the samples are at higher temperatures. To overcome this limitation and to expand the temperature range for the certification process, platinum/palladium thermocouples were incorporated in the measurement setup. This paper discusses the influence of the different differential thermocouples used for the measurement of the Seebeck coefficients. Results of a comparative investigation of Seebeck coefficient measurements of a metallic and two semiconducting reference materials in the temperature range from 300 K to 870 K are presented.