Mg2Si基热电材料的稀土掺杂优化

采用机械研磨-电场激活压力辅助合成(FAPAS)技术,快速合成了稀土Sc和Y掺杂的Mg2Si基热电材料,所得试样组织均匀、致密,试样的平均晶粒尺寸为1.5～2μcm,微量稀土元素不改变基体材料的组织形貌.分析表明两种稀土元素均在不同程度改善热电性能,其中掺杂0.427%(摩尔分数)Sc和0.173%(摩尔分数)Y的试样...     

能带优化和载流子调控改善SnTe的热电性能

作为ⅣA族碲化物,SnTe具有与PbTe相同的晶体结构和相似的双价带结构,是一种非常有前途的热电材料,但高温软化和低温热电性能差等问题阻碍了其进一步推广应用。因此,提升SnTe的平均热电优值,拓宽服役区间,有重要的研究意义。能带工程和晶格工程可同时优化功率因子和晶格热导率,提升SnTe的热电性能。本研究采用MgSe合金化策略,通过熔炼和放电等离子烧结(SPS)的方法制备了一系列Sn_1-yPb_yTe-x%MgSe(0.01≤y≤0.05,0≤x≤6)样品。研究发现,合金化MgSe可增大能带带隙,有效抑制本征SnTe在高温段的双极扩散,使高温Seebeck系数得到提升,同时声子散射降低了体系晶格热导率,使高温热电性能(873 K)提升了100%;掺杂Pb元素可有效调制载流子浓度抑制电子热导率,从而提升SnTe平均热电性能。其中,Sn_0.96Pb_0.04Te-4%MgSe样品在873 K的ZT为1.5,423～873 K的平均ZT达到0.8,得到了比文献更优异的结果。     

机械合金化和放电等离子烧结制备AgPbSbTe热电材料

采用机械合金化和放电等离子烧结方法制备高性能AgPbSbTe热电材料,研究了制备工艺对材料热电性能的影响。结果表明,材料的物相组成和热电性能都受到机械合金化时间的影响;适当地控制放电等离子烧结工艺可以抑制晶粒长大,增加晶界散射,降低热导率。实验中得到AgPbSbTe热电材料的最大功率因子为18μW/K~2cm,最小热导率为1.1 W/m K。机械合金化(球磨4 h、转速350 r/m)并在673 K放电等离子烧结5 min,得到AgPbSbTe材料的最大热电优值ZT为1.2(700 K)。     

球磨时间对P型Bi2Te3基热电材料性能的影响

采用区熔法和机械球磨（MM）与放电等离子烧结（SPS）技术相结合制备P型Bi2Te3基热电材料。在300-423K的温度范围内测试了样品的电导率、Seebeck系数和热导率。系统研究了球磨时间对合金化与热电性能的影响。球磨10h的样品在室温时具有最低的热导率，因此其热电优值高于其它样品，在室温时达到最大值0．995。     

Bi-Te基热电材料的研究进展

阐述了Bi2Te3热电材料的基本特性,评述了Se,TeL,SiC,RE(La,Ce等)的掺杂对BiTe材料热电性能的影响,以及国内外掺杂Bi-Te基热电材料的研究进展.介绍了Bi-Te基合金的制备技术的发展.最后指出通过材料的结构优化、组分调整及制备技术的改进,可以进一步提高材料的热电性能,得到理想的热电优值.     

Mg2Si基热电材料研究现状及进展

介绍了热电材料的基本原理与应用情况,总结了现阶段提高Mg2Si基热电材料热电性能的途径：包括对Mg2Si材料进行多种元素的掺杂;制备低维数材料、纳米材料与超晶格结构材料。评述了Mg2Si基热电材料在掺杂改性和制备方面的研究进展。分别阐述了掺杂Ge、Sn、Pb、Te、Sb、Bi、Ag等几种元素对Mg2Si热电性能的影响。对溶体生长法、固相烧结法、机械合金化、放电等离子烧结法与电场激活压力辅助合成法的优缺点进行了评价,通过对比最后指出了场激活压力辅助合成法是新的合成Mg2Si节能和高效的新的制备方法。     

基于分步式双重调控n型(PbTe)1-x-y(PbS)x(Sb2Se3)y体系的热电传输特性

PbTe在中温区热电材料中广受关注, 然而, n型PbTe因其较低的载流子浓度和复杂的能带结构, 其热电性能难以大幅提升。本研究通过分步式添加PbS、Sb₂Se₃组元以调控n型PbTe基体的热、电传输性能。研究发现, PbS与Sb₂Se₃组元可分别提升功率因子和降低热导率。通过扩大带隙、增加点缺陷、第二相弥散等途径可改善能带, 加剧散射, 从而有效提升热电优值ZT。其中(PbTe)_0.94(PbS)_0.05(Sb₂Se₃)_0.01表现出最佳的热电性能, 700 K时ZT最大值为1.7, 且ZT平均值较PbTe基体显著提高, 这表明分步式双组元调控可为改善其它材料体系的热电性能提供技术途径。     

Bi-Te基薄膜热电材料的研究进展

热电材料是一种能够实现热能与电能直接转换的功能材料,由于无法有效降低块体热电材料的热导率,其性能研究进展缓慢.自上世纪90年代初Hicks等提出了低维化能够显著提高热电材料性能的理论后,薄膜热电材料开始受到广泛关注.低维化提高材料性能的原因主要是材料在低维化后能够产生量子限制效应,使得电子在被压缩维度的运动受到限制.首先,在费米能级附近,与Seebeck系数呈正相关的电子态密度会增大,导致低维热电材料的Seebeck系数相比块体材料显著增大.其次,与块体材料相比,薄膜材料存在更多能够散射声子的晶界,能有效降低晶格热导率.在这两种效应的共同作用下,材料的热电优值(ZT值)能够显著增大.低维热电材料的研究初期主要是通过数学模型和数值计算,从理论上证明量子效应会影响材料的Seebeck系数和电导率,且能实现二者的独立控制,从而提高材料的ZT值.后期的实验数据证明,通过合适的热处理工艺能够有效降低薄膜材料的缺陷,提高其综合性能.因此,热处理工艺的改进对性能的提升也非常重要.热电材料性能的提升离不开制备工艺的进步.为了获得低维化的热电材料,多种薄膜材料制备工艺被用于样品的制备,且不同的制备工艺各有优缺点.Bi-Te基合金不仅可用于低温发电还可用于低温制冷,是目前应用最广泛的低温热电材料,虽然其块体状态下的热电性能研究已趋于完善,但其薄膜状态下热电性能的理论研究还相差甚远,因此Bi-Te基低温薄膜热电材料成为研究热点.本文介绍了国内外采用不同制备工艺生长Bi-Te基热电薄膜材料的发展状况以及热电性能测试方法,提出了在目前发展薄膜热电材料时需要重点关注的方面,并对低维热电材料的发展方向进行了阐述.     

Sn基Ⅷ型笼合物Ba_8Ga_(16)Sn_(30)热电材料研究进展

Ⅷ型Sn基笼合物Ba8Ga16Sn30由于具有优异的热电传输特性而被认为是最具有应用前景的热电材料之一。介绍了Ⅷ型Sn基笼合物的晶体结构、合成方法及理论和实验方面的研究情况,并对有关研究进展进行评述,同时提出进一步研究该笼合物的一些建议。     

Ca(Na)-Co-O基热电氧化物研究进展

介绍了钴基氧化物热电材料研究现状及前景.重点介绍了具有潜力的Na/Ca-Co-O热电氧化物材料的结构、热电性能特征、制备等研究现状;并对Na/Ca-Co-O基热电氧化物Na/Ca位和Co位掺杂研究进行了评述;最后指出了钴基氧化物热电材料的应用前景和研究方向.     

氧化物热电材料的研究现状

氧化物热电材料具有耐高温、抗氧化、使用寿命长、环境友好等特点，并且制备工艺简单，品种多，具有良好的发展前景。本文介绍了层状金属氧化物、钙钛矿复合型氧化物、透明导电氧化物（TCO）、低维氧化物、超晶格氧化物等各种热电氧化物材料，综述了各类氧化物材料目前研究现状、影响该类材料热电性能的各种因素以及有效提高材料的热电性能的途径。     

低维纳米热电材料研究进展

低维纳米热电材料具有优良的热电性能,近年来受到大量研究者的喜爱。本文讨论低维纳米热电材料的机理,综述了零维纳米热电材料、一维纳米热电材料、二维纳米热电材料的最新研究进展,为低维纳米热电材料的进一步深入研究做了初步的总结和预测。     

New Directions for Low‐Dimensional Thermoelectric Materials

Many of the recent advances in enhancing the thermoelectric figure of merit are linked to nanoscale phenomena found both in bulk samples containing nanoscale constituents and in nanoscale samples themselves. Prior theoretical and experimental proof‐of‐principle studies on quantum‐well superlattice and quantum‐wire samples have now evolved into studies on bulk samples containing nanostructured constituents prepared by chemical or physical approaches. In this Review, nanostructural composites are shown to exhibit nanostructures and properties that show promise for thermoelectric applications, thus bringing together low‐dimensional and bulk materials for thermoelectric applications. Particular emphasis is given in this Review to the ability to achieve 1) a simultaneous increase in the power factor and a decrease in the thermal conductivity in the same nanocomposite sample and for transport in the same direction and 2) lower values of the thermal conductivity in these nanocomposites as compared to alloy samples of the same chemical composition. The outlook for future research directions for nanocomposite thermoelectric materials is also discussed.     

Toward Ultrahigh Thermoelectric Performance of Cu2SnS3-Based Materials by Analog Alloying

Cu₂SnS₃ is a promising thermoelectric candidate for power generation at medium temperature due to its low-cost and environmental-benign features. However, the high electrical resistivity due to low hole concentration severely restricts its final thermoelectric performance. Here, analog alloying with CuInSe₂ is first adopted to optimize the electrical resistivity by promoting the formation of Sn vacancies and the precipitation of In, and optimize lattice thermal conductivity through the formation of stacking faults and nanotwins. Such analog alloying enables a greatly enhanced power factor of 8.03 µW cm⁻¹ K⁻² and a largely reduced lattice thermal conductivity of 0.38 W m⁻¹ K⁻¹ for Cu₂SnS₃ – 9 mol.% CuInSe₂. Eventually, a peak ZT as high as 1.14 at 773 K is achieved for Cu₂SnS₃ – 9 mol.% CuInSe₂, which is one of the highest ZT among the researches on Cu₂SnS₃-based thermoelectric materials. The work implies analog alloying with CuInSe₂ is a very effective route to unleash superior thermoelectric performance of Cu₂SnS₃.     

Alloying behaviour in nanocrystalline materials during mechanical alloying

The alloying behaviour in a number of systems such as Cu-Ni, Cu-Zn, Cu-Al, Ni-Al, Nb-Al has been studied to understand the mechanism as well as the kinetics of alloying during mechanical alloying (MA). The results show that nanocrystallization is a prerequisite for alloying in all the systems during MA. The mechanism of alloying appears to be a strong function of the enthalpy of formation of the phase and the energy of ordering in case of intermetallic compounds. Solid solutions (Cu-Ni), intermetallic compounds with low ordering energies (such as Ni₃Al which forms in a disordered state during MA) and compounds with low enthalpy of formation (Cu-Zn, Al₃Nb) form by continuous diffusive mixing. Compounds with high enthalpy of formation and high ordering energies form by a new mechanism christened as discontinuous additive mixing. When the intermetallic gets disordered, its formation mechanism changes from discontinuous additive mixing to continuous diffusive one. A rigorous mathematical model, based on iso-concentration contour migration method, has been developed to predict the kinetics of diffusive intermixing in binary systems during MA. Based on the results of Cu-Ni, Cu-Zn and Cu-Al systems, an effective temperature (T _eff) has been proposed that can simulate the observed alloying kinetics. TheT _eff for the systems studied is found to lie between 0·42–0·52T ₁.     

Extraordinary Thermoelectric Performance Realized in n‐Type PbTe through Multiphase Nanostructure Engineering

Lead telluride has long been realized as an ideal p‐type thermoelectric material at an intermediate temperature range; however, its commercial applications are largely restricted by its n‐type counterpart that exhibits relatively inferior thermoelectric performance. This major limitation is largely solved here, where it is reported that a record‐high ZT value of ≈1.83 can be achieved at 773 K in n‐type PbTe‐4%InSb composites. This significant enhancement in thermoelectric performance is attributed to the incorporation of InSb into the PbTe matrix resulting in multiphase nanostructures that can simultaneously modulate the electrical and thermal transport. On one hand, the multiphase energy barriers between nanophases and matrix can boost the power factor in the entire temperature range via significant enhancement of the Seebeck coefficient and moderately reducing the carrier mobility. On the other hand, the strengthened interface scattering at the intensive phase boundaries yields an extremely low lattice thermal conductivity. This strategy of constructing multiphase nanostructures can also be highly applicable in enhancing the performance of other state‐of‐the‐art thermoelectric systems.     

AgSn18SbTe20无铅中温热电材料的粉末冶金法制备工艺及其对性能的影响

研究了制备p型AgSn₁₈SbTe₂₀无铅热电材料的机械合金化(MA)结合放电等离子烧结(SPS)工艺, 调查了MA过程中球磨时间和SPS温度对材料电热传输性能和热电优值的影响, 分析了样品的物相和显微结构。研究表明, 适当延长球磨时间和降低烧结温度, 可以有效提高材料的热电性能。优化制备条件可以实现59%的性能提升, 最佳条件(球磨12 h、SPS温度743 K)下制备的样品ZT值在723 K达到0.62。