GaInX_3(X=S,Se,Te):Ultra-low thermal conductivity and excellent thermoelectric performance

Seeking intrinsically low thermal conductivity materials is a viable strategy in the pursuit of high-performance thermoelectric materials.Here,by using first-principles calculations and semiclassical Boltzmann transport theory,we systemically investigate the carrier transport and thermoelectric properties of monolayer Janus GaInX_(3)(X=S,Se,Te).It is found that the lattice thermal conductivities can reach values as low as 3.07 W·m^(-1)·K^(-1),1.16 W·m^(-1)·K^(-1)and 0.57 W·m^(-1)·K^(-1)for GaInS_(3),GaInSe_(3),and GaInTe_(3),respectively,at room temperature.This notably low thermal conductivity is attributed to strong acoustic-optical phonon coupling caused by the presence of low-frequency optical phonons in GaInX_(3) materials.Furthermore,by integrating the charac teristics of electronic and thermal transport,the dimensionless figure of merit ZT can reach maximum values of 0.95,2.37,and 3.00 for GaInS_(3),GaInSe_(3),and GaInTe_(3),respectively.Our results suggest that monolayer Janus GaInX_(3)(X=S,Se,Te)is a promising candidate for thermoelectric and heat management applications.

Design,preparation,application of advanced array structured materials and their action mechanism analyses for high performance lithium-sulfur batteries

Lithium-sulfur battery(LSB)has brought much attention and concern because of high theoretical specific capacity and energy density as one of main competitors for next-generation energy storage systems.The widely commercial application and development of LSB is mainly hindered by serious“shuttle effect”of lithium polysulfides(Li PSs),slow reaction kinetics,notorious lithium dendrites,etc.In various structures of LSB materials,array structured materials,possessing the composition of ordered micro units with the same or similar characteristics of each unit,present excellent application potential for various secondary cells due to some merits such as immobilization of active substances,high specific surface area,appropriate pore sizes,easy modification of functional material surface,accommodated huge volume change,enough facilitated transportation for electrons/lithium ions,and special functional groups strongly adsorbing Li PSs.Thus many novel array structured materials are applied to battery for tackling thorny problems mentioned above.In this review,recent progresses and developments on array structured materials applied in LSBs including preparation ways,collaborative structural designs based on array structures,and action mechanism analyses in improving electrochemical performance and safety are summarized.Meanwhile,we also have detailed discussion for array structured materials in LSBs and constructed the structure-function relationships between array structured materials and battery performances.Lastly,some directions and prospects about preparation ways,functional modifications,and practical applications of array structured materials in LSBs are generalized.We hope the review can attract more researchers'attention and bring more studying on array structured materials for other secondary batteries including LSB.

Control of interfacial reaction and defect formation in Gd/Bi_(2)Te_(2.7)Se_(0.3) composites with excellent thermoelectric and magnetocaloric properties

The method to combine thermoelectric(TE)and magnetocaloric(MC)cooling techniques lies in developing a new material that simultaneously possesses a large TE and good MC cooling performance.In this work,using n-type Bi_(2)Te_(2.7)Se_(0.3)(BTS)as the TE base material and Gd as the second-phase MC material,Gd/BTS composites were prepared by the spark plasma sintering method.In the composites,interfacial reaction between Gd and BTS was identified,resulting in the formation of Gd Te,which has a large impact on the electron concentration through the adjustment of defect concentration.The MC/TE composite containing 2.5 wt%Gd exhibited a ZT value of 0.6 at 300 K,essentially retaining the original TE performance,while all the composites largely maintained the excellent MC performance of Gd.This work provides a potential pathway to achieving high performance in MC/TE composites.

The preparation and properties of N-doped carbon materials and their use for sodium storage

Defect engineering by heteroatom doping gives carbon materials some new characteristics such as a different electronic structure and a high electrochemical activity,making them suitable for high-performance applications.N-doping has been widely investigated because of its similar atom radius to carbon,high electronegativity as well as many different configurations.We summarize the preparation methods and properties of N-doped carbon materials,and discuss their possible use in sodium ion storage.The relationships between N content/configuration and crystallinity,electronic conductivity,wettability,chemical reactivity as well as sodium ion storage performance are discussed.

A New Technology to Measure the Thermoelectric Performance of Nanowire Array Structure

Recently, the study on one-dimensional thermoelectric materials is getting more and more attention. For those one-dimensional thermoelectric materials with nanowire array structure fabricated with alumina film as template, its thickness is often in the range of 10 to several tens micrometers, and the conventional measurement cannot be used. The key difficulties of the thermoelectric performance measurement for nanowire array materials include two aspects: 1) How to heat the two sides of the specimen uniformly and keep the temperature difference constantly at the same time; 2) How to measure the temperature of the two sides of the specimen with the thickness of 10 to several tens micrometers. A new type heating and temperature measuring technology has been used, and it can be simply described as liquid heating and separate temperature measurement. According to this principle, a thermoelectric performance measurement system has been established.

Fabrication and property of high-performance Ag-Pb-Sb-Te system semiconducting thermoelectric materials

High performance Ag-Pb-Sb-Te system thermoelectric bulk materials were fabricated by a combination of mechanical alloying (MA) and spark plasma sintering (SPS). Phase composition and microstructure of the resultant materials were investigated by X-ray diffraction (XRD) and scanning electron micros-copy (SEM) analysis. A special emphasis was paid to the effects of chemical composition, especially the Pb content on the thermoelectric properties of the Ag0.8Pb18+xSbTe20 samples, including electrical resistivity, Seebeck coefficient, power factor, thermal conductivity and dimensionless figure of merit. The present study reveals that the optimal composition of Ag0.8Pb18+xSbTe20 samples is Ag0.8Pb22.5SbTe20 and the maximum figure of merit (ZT) is 1.2 at 673 K.

Realizing high thermoelectric performance in hot-pressed polycrystalline Al_(x)Sn_(1-x) Se through band engineering tuning

SnSe-based thermoelectric materials are being explored since they have potential high thermoelectric figure of merit.We synthesized polycrystalline Al_(x)Sn_(1-x)Se(x=0.01,0.02,0.03 and 0.04)by hot-pressing method,and combined theoretical estimation with experimental measurement to investigate the in-fluence of Al doping on thermoelectric properties of SnSe.It was found that dopant Al can effectively adjust the band structure of SnSe by introducing intermediate band.Al doping with low content(x=0.01 and 0.02)can introduce a single intermediate band close to the valence band maximum or conduction band minimum,achieving band engineering optimization.In high temperature region(498 K<T<823 K),the electronic transport properties significantly enhance with thermal excitation.The lattice thermal conductivity reduces with the Al atomic point defect scattering,leading to a low thermal conductivity of 0.47 W m^(-1) K^(-1) in Al_(0.04)Sn_(0.96)Se at 823 K.As a result,a high ZT of 0.84 at 823 K is obtained from the Al_(0.04)Sn_(0.96) Se perpendicular to the pressing direction,which is 58.5%larger than that of SnSe.In addition,dopant Al can adjust the anisotropy of polycrystalline SnSe.The anisotropy of electronic properties are enhanced with low doping level(x=0.01,0.02)and suppressed with high doping level(x=0.03,0.04).

Thermal stability and thermoelectric properties of Cd-doped nano-layered Cu2Se prepared using NaCl flux method

Cu2Se is a promising"phonon liquid-electron crystal"thermoelectric material with excellent thermoelectric performance.In this work,Cd-doped Cu2-xSeCdx(x=0,0.0075,0.01,and 0.02)samples were prepared using NaCl flux method.The solubility of Cd in Cu2Se at room temperature was less than 6%,and a second phase of CdSe was found in the samples with large initial Cd content(x=0.01 and 0.02).Field-emission scanning electron microscopic image showed that the arranged lamellae formed a large-scale layered structure with an average thickness of approximately 100 nm.Transmission electron microscopy demonstrated that doping of Cd atoms did not destroy the crystal integrity of Cu2Se.A small amount of Cd in Cu2Se could reduce the electrical and thermal conductivities of the material,thus significantly enhancing its thermoelectric performance.With the increase in Cd content in the sample,the carrier concentration decreased and the mobility increased gradually.Thermogravimetric differential thermal analysis showed that no weight loss occurred below the melting point.Excessive Cd doping led to the emergence of the second phase of CdSe in the sample,thus significantly increasing the thermal conductivity of the material.A maximum ZT value of 1.67 at 700 K was obtained in the Cu1.9925SeCd0.0075 sample.

Thermoelectric Properties of n-type Poly(nickel 1,1,2,2-ethenetetrathiolate)Prepared by a New One-step Solvothermal Method

Poly(nickel 1,1,2,2-ethenetetrathiolate)(poly[Na_(x)(Ni-ett)])is one of the most promising n-type organic thermoelectric materials which can be used in wearable devices.However,the conventional solution method is time-consuming and the prepared poly[Na_(x)(Ni-ett)]usually has poor crystallinity,which does not benefit for achieving high thermoelectric performance.Here,a new one-step solvothermal method under the high reaction temperature and high vapor pressure was developed to prepare poly[Na_(x)(Ni-ett)]with a quite short period.The experimental results show crystallinity and electrical conductivity are greatly enhanced as compared with those prepared by conventional solution method.As a result,a maximum ZT value of 0.04 was achieved at 440 K,which is about four times of the polymer prepared by the conventional solution method.This study may provide a new route to enhance the TE properties of n-type organic thermoelectric materials.

Thermoelectric Characterization of (Na_(1-y)M_y)_(1.6)Co_2O_4(M=K, Ca, Sr)

Oxide materials NaCo2O4 and （Na1-yMu）1.6Co2O4 （M=K, 0.05≤y≤0.35; M=Ca, St, 0.10≤y≤0.40） were prepared by a sol-gel method. Experimental resultS indicated that the Seebeck coefficient and the Powerfactor of NaCo2O4 were improved by doping Ca and Sr but not by K. The Power-factor of NaCo2O4 is in its maximum, 1.68×10^-4 W·m^-1·K^-2 and 11% bigger than that of the original one when the dopant fraction of Ca was 0.1. Doping Sr makes NaCo2O4 have the biggest Power-factor, 1.68×10^-4 W·m^-1·K^-2 that is 50% bigger than the non-doping oxide. The experimental results indicate that suitable dopants and addition amounts could improve the thermoelectric properties of NaCo2O4 greatly.

Recent advances in organic,inorganic,and hybrid thermoelectric aerogels

The thermoelectric(TE)materials and corresponding TE devices can achieve direct heat-to-electricity conversion,thus have wide applications in heat energy harvesting(power generator),wearable electronics and local cooling.In recent years,aerogel-based TE materials have received considerable attention and have made remarkable progress because of their unique structural,electrical and thermal properties.In this review,the recent progress in both organic,inorganic,and composite/hybrid TE aerogels is systematically summarized,including the main constituents,preparation method,TE performance,as well as factors affecting the TE performance and the corresponding mechanism.Moreover,two typical aerogel-based TE devices/generators are compared and analyzed in terms of assembly modes and output performance.Finally,the present challenges and some tentative suggestions for future research prospects are provided in conclusion.

Enhancement of thermoelectric properties of SrTiO3/LaNb–SrTiO3 composite by different doping levels

Strontium titanate（STO）is an n-type oxide thermoelectric material,which has shown great prospects in recent years.The doping of La and Nb into STO can improve its power factor,whereas its thermal conductivity is still very high.Thus,in order to obtain a high thermoelectric figure-of-merit z T,it is very important to reduce its thermal conductivity.In this paper,using a combination of a hydrothermal method and a high-efficiency sintering method,we succeed in preparing a composite of pure STO and La Nb-doped STO,which simultaneously realizes lower thermal conductivity and higherSeebeck coefficient,therefore,the thermoelectric properties of STO are significantly improved.In the SrTiO3/La Nb–SrTiO3 bulk samples,the lowest thermal conductivity is 2.57 W·m^-1·K^-1 and the highest z T is 0.35 at 1000 K for the STO/La（10）Nb（20）–STO sample.

Thermoelectric field for a coated hole of arbitrary shape in a nonlinearly coupled thermoelectric material

We study the thermoelectric field for an electrically and thermally insulated coated hole of arbitrary shape embedded in an infinite nonlinearly coupled thermoelectric material subject to uniform remote electric current density and uniform remote energy flux.A conformal mapping function for the coating and matrix is introduced,which simultaneously maps the hole boundary and the coating-matrix interface onto two concentric circles in the image plane.Using analytic continuation,we derive a general solution in terms of two auxiliary functions.The general solution satisfies the insulating conditions along the hole boundary and all of the continuity conditions across the perfect coating-matrix interface.Once the two auxiliary functions have been obtained in the elementary-form,the four original analytic functions in the coating and matrix characterizing the thermoelectric fields are completely and explicitly determined.The design of a neutral coated circular hole that does not disturb the prescribed thermoelectric field in the thermoelectric matrix is achieved when the relative thickness parameter and the two mismatch parameters satisfy a simple condition.Finally,the neutrality of a coated circular thermoelectric inhomogeneity is also accomplished.

Combinatorial screening via high-throughput preparation:Thermoelectric performance optimization for n-type Bi-Te-Se film with high average zT>1

Thermoelectric materials have drawn extensive interest due to the direct conversion between electricity and heat,however,it is usually a time-consuming process for applying traditional“sequential”meth-ods to grow materials and investigate their properties,especially for thermoelectric films that typically require fine microstructure control.High-throughput experimental approaches can effectively accelerate materials development,but the methods for high-throughput screening of the microstructures require further study.In this work,a combinatorial high-throughput optimization solution of material properties is proposed for the parallel screening and optimizing of composition and microstructure,which involves two distinctive types of high-throughput fabrication approaches for thin films,along with a new portable multiple discrete masks based high-throughput preparation platform.Thus,Bi_(2)Te_(3-x)Se_(x)thin film library with 196 throughputs for locating the optimized composition is obtained in one growth cycle.In addition,another thin film library composed of 31 materials with traceable process parameters is built to further investigate the relationship between microstructure,process,and thermoelectric performance.Through high-throughput screening,the Bi_(2)Te_(2.9)Se_(0.1)film with(00l)orientation is prepared with a peak zT value of 1.303 at 353 K along with a high average zT value of 1.047 in the interval from 313 to 523 K.This method can be also extended to the discovery of other functional thin films with a rapid combinatorial screening of the composition and structure to accelerate material optimization.

Ti_(3)SiC_(2)陶瓷材料制备方法研究进展

作为MAX相家族重要成员,钛硅化碳Ti_(3)SiC_(2)除了具有耐高温、抗氧化性能外,还具有与金属类似的优异导电性、导热性和可加工性,在电接触材料、热交换器构件材料、润滑材料等领域展现出较大的应用潜力,成为当前一种备受关注的新型陶瓷材料。现有的Ti_(3)SiC_(2)制备方法主要有无压烧结、热压烧结、热等静压、放电等离子烧结、前驱体转换陶瓷、反应熔体浸渗法、熔盐法、化学气相沉积、物理气相沉积等。本文首先阐述了Ti_(3)SiC_(2)材料的结构与性能,然后重点综述了国内外Ti_(3)SiC_(2)陶瓷材料的制备方法,最后展望了Ti_(3)SiC_(2)陶瓷材料的应用前景。

The on-chip thermoelectric cooler:advances,applications and challenges

With the development of 5G technology and increasing chip integration,traditional active cooling methods struggle to meet the growing thermal demands of chips.Thermoelectric coolers(TECs)have garnered great attention due to their rapid response,significant cooling differentials,strong compatibility,high stability and controllable device dimensions.In this review,starting from the fundamental principles of thermoelectric cooling and device design,high-performance thermoelectric cooling materials are summarized,and the progress of advanced on-chip TECs is comprehensively reviewed.Finally,the paper outlines the challenges and opportunities in TEC design,performance and applications,laying great emphasis on the critical role of thermoelectric cooling in addressing the evolving thermal management requirements in the era of emerging chip technologies.

电臂尺寸和安装条件对热电模块力学性能的影响

针对热电制冷模块中热电臂尺寸对模块整体热应力场的影响,以C-31106型热电制冷模块为研究对象,建立由31对热电偶组成的热-电-力学耦合多物理场模型.采用有限元仿真方法,考虑钎料层的存在并引入表征黏塑性材料的Anand修正本构方程,建立3种安装条件下的热电模型,分析不同电流下热电臂高度和截面边长对热电模块温度场和力学性能的影响规律.结果表明,当热电臂处于最佳高度时,在给定范围内热电臂截面边长越大,越有利于提高热电模块力学可靠性,当工作电流为2.6 A,截面边长从0.99 mm增加到1.09 mm时,冷、热端的最大von Mises应力分别减小了74.67%和22.60%.对模块冷端和热端分别采用固定约束和机械压装的安装方式可有效提高热电模块的力学可靠性,当采用上述安装方式时,冷、热端的最大von Mises应力相比两端只采用固定约束的安装方式分别减小了48.76%和74.02%.

基于准稳态法的热电材料变物性参数表征测量方法

温差发电技术能够实现热能到电能的直接转换,在余热利用、航天器供电和自供电传感器等领域具有广泛应用,其核心之一是用于实现热-电转换的热电材料。热电材料物性参数的表征在热电器件应用、优化设计、故障诊断等研究中有重要意义。目前大多数热电材料物性参数表征方法认为材料的热电参数为常数,忽视了热电参数与温度非线性相关,且没有全面考虑器件中的接触电阻和热阻。该文提出一种基于准稳态法和热电器件测试装置的热电材料变物性参数表征测量方法:首先提出准稳态法对材料物性参数的表征计算方法,通过仿真验证了该方法的正确性;在此基础上,结合热电器件测试装置,采用实验对热电材料进行了变物性参数表征,结果表明,测试结果与厂家参数的最大误差仅为4.3%,能够实现对热电参数的准确表征。该方法实现了在更宽的温度范围内对热电材料物理参数的准确表征,丰富了热电器件测试装置的功能,能够降低材料测试装置的设备投入和测试成本。

Bi_(2)Te_(3)/KOH/PEDOT:PSS和SiO_(2)气凝胶增强钢丝绒热电性能研究

在热电材料研究领域,一般认为金属的Seebeck系数较低,因此有关金属的热电性能的研究并不多见。但研究发现金属的物理形态对其热电性能具有影响。考察了金属纤维钢丝绒(SW)的热电性能。发现SW(主要成分为Fe)的Seebeck系数是块体铁的2倍。在此基础上,将SW与有机和无机热电材料进行复合,并在其空隙中填充SiO_(2)气凝胶,最终制备出了Bi_(2)Te_(3)/KOH/PEDOT:PSS@SW-SiO_(2)气凝胶复合材料,使其热电性能得到了进一步提升。结果表明,气凝胶的加入可使SW的导热系数降低34%。电导率(σ)、热导率(κ)和Seebeck系数(S)得到解耦。Bi_(2)Te_(3)/KOH/PEDOT:PSS@SW-SiO_(2)气凝胶的Seebeck系数、热电优值(ZT)和功率因子(PF)分别是纯SW的1.2、3.4、2.4倍。通过改变材料物理形态和添加气凝胶来提高材料热电性能的方式有望为其他热电材料的研究提供新的思路和有益参考。

高熵热电材料的研究进展

高熵合金具有许多诸如高强度、高硬度、抗氧化等优异的性能,使它在诸多领域有着广泛的应用。随着高熵合金的广泛应用,通过多主元成分设计,增加构型熵,利用高熵合金的特性也被用来调控热电材料的性能。综述了常见的高熵热电材料的发展现状,分析高熵对热电性能的解耦前景。通过分析Ⅳ-Ⅵ族热电材料、类液态材料、Half-heusler合金等材料中熵工程的应用,总结了高熵对热电性能的影响。通过合金化、高熵效应,结合类液效应、固溶量、共振掺杂、纳米沉淀和构建自适应亚晶格等调控手段,可以显著改善热电材料的性能,并为发展更为高效的热电转换材料提供了新的方向。