热电物理的研究进展

热电效应在发电，致冷方面有巨大的应用潜力，这些年来，人们为提高热电能量转换效率进行了不懈的努力，文章概述了从机理上提高材料热性能的一般途径，在此基础上，介绍了最近几年在氧化物超导体，ＴＰｎ３化合物，富硼固体等新材料体系中，以及在非均匀材料，复合型材料，量子阱结构等新形式材料中的研究结果。     

机器学习在热电材料领域的应用

在追求可持续发展的未来,热电材料是不可或缺的.它在全固态发电和制冷方面具有十分广泛的应用前景.在过去的几十年间,人们一直致力于寻找新型高性能热电材料.然而,传统的实验试错法效率较低,限制了新材料的研究步伐.机器学习作为一种具有强大数据分析能力的方法,近年来已越来越多地应用于热电材料的研究.这篇综述总结了热电材料研究领域常用的机器学习方法,系统地介绍了它们在材料结构、电子和热电输运等性质上的应用案例和相关研究进展,并对该领域的发展前景进行了展望.     

Thermoelectric properties of Bi2Se3/Bi2Te3/Bi2Se3 and Sb2Te3/Bi2Te3/Sb2Te3 quantum well systems

In this work, we develop a theory of thermoelectric transport properties in two-dimensional semiconducting quantum well structures. Calculations are performed for n-type 0.1 wt.% CuBr-doped Bi₂Se₃/Bi₂Te₃/Bi₂Se₃ and p-type 3 wt.% Te-doped Sb₂Te₃/Bi₂Te₃/Sb₂Te₃ quantum well systems in the temperature range 50–600 K. It is found that reducing the well thickness has a pronounced effect on enhancing the thermoelectric figure of merit (ZT). For the n-type Bi₂Se₃/Bi₂Te₃/Bi₂Se₃ with 7 nm well width, the maximum value of ZT is estimated to be 0.97 at 350 K and for the p-type Sb₂Te₃/Bi₂Te₃/Sb₂Te₃ with well width 10 nm the highest value of the ZT is found to be 1.945 at 440 K. An explanation is provided for the resulting higher ZT value of the p-type system compared to the n-type system.     

PbTe纳米晶高压热电性能的研究

 利用自建的400 t四柱双缸液压机,研究了PbTe纳米晶在0~0.8 GPa压力范围内热电性能随压力的变化。实验结果表明：PbTe纳米晶电导率随压力的增加而增加,而热电动势随压力的增加而减小,两者随压力的变化具有可逆性;PbTe纳米晶具有极高的热电动势,在常压下达到565 μV/K,在0.8 GPa压力下,材料的电导率为常压下的4倍,热电动势仅降低20%,功率因子则达到常压下的3倍。研究表明,高压能显著提高PbTe纳米晶的热电性能。利用第一性原理计算了0.4~4.0 GPa压力范围内材料的简约费米能级,计算结果与实验结果相吻合。     

热电材料室温下塞贝克系数测试装置的研制

提出一种测试热电材料室温下塞贝克系数的有效方法并搭建了其测试装置。该测试装置通过电路控制获得标准温差实现塞贝克系数的精确测量,其特点是利用电路控温取代传统的恒温循环水和温度测试仪表控温系统,结构简单、操作方便、成本低廉。     

Thermoelectric effects through weakly coupled double quantum dots

The electrical conductance, the thermal conductance, the thermopower and the thermoelectrical figure of merit are analyzed through a double quantum dot system weakly coupled to metal electrodes, by means of density matrix approach. The effects of interdot tunneling, intra- and interdot Coulomb repulsions on the figure of merit are examined. Results show that increase of interdot tunneling gives rise to a reduction in figure of merit. On the other hand, increase of Coulomb repulsion results in enhancement of figure of merit because of reduce of bipolar effect.     

Sn1-xGexTe的高温高压合成及热电性能

在众多热电材料中,SnTe具有与PbTe相同的晶体结构且不含重金属Pb,近年来引起了人们的广泛关注。目前,本征SnTe的热电性能并不特别优异,存在以下问题:大量本征Sn空位导致载流子浓度过高,从而降低了电输运性能;价带中的轻带与重带能量劈裂较大,且带隙过窄,不利于通过重带参与电运输提高Seebeck系数;晶格热导率较大。利用高温高压方法快速合成了Ge掺杂的SnTe合金,系统研究了不同Ge含量对SnTe的微观结构和热电性能的影响。结果表明:Ge掺杂能够有效地调控SnTe材料的电运输性能;Ge掺杂使样品的微观结构发生变化,样品晶粒细化,且析出纳米第二相,晶界和纳米相对声子的散射作用降低了热导率;样品Ge_0.2Sn_0.8Te在700 K时的热电优值达到0.35。     

Advances in thermoelectric (GeTe)x(AgSbTe2)100-x

The (GeTe)_x(AgSbTe₂)_100-x alloys, also called TAGS-x in short, have long been demonstrated as a promising candidate for thermoelectric applications with successful services as the p-type leg in radioisotope thermoelectric generators for space missions. This largely stems from the complex band structure for a superior electronic performance and strong anharmonicity for a low lattice thermal conductivity. Utilization of the proven strategies including carrier concentration optimization, band and defects engineering, an extraordinary thermoelectric figure of merit, zT, has been achieved in TAGS-based alloys. Here, crystal structure, band structure, microstructure, synthesis techniques and thermoelectric transport properties of TAGS-based alloys, as well as successful strategies for manipulating the thermoelectric performance, are surveyed with opportunities for further advancements. These strategies involved are believed to be in principle applicable for advancing many other thermoelectrics.     

高压烧结对n型PbTe基材料热电性能的影响

 采用高压烧结技术制备了按偏离化学计量比配制的PbTe基热电材料（Pb_0.55Te_0.45）,重点研究了烧结压力对材料热电性能的影响。研究结果表明：高压烧结过程能有效降低材料中的晶格缺陷,从而显著改变样品中的载流子浓度及其迁移率。与未经烧结的常压熔融样品相比,高压烧结样品的Seebeck系数得到大幅提高,电导率略有降低,室温热导率降低了50%,所以高压烧结样品的品质因子得到较大提高。当烧结压力为2 GPa时,所得样品在700 K时其品质因子达到0.59,相比未经烧结的常压熔融样品提高了150%。     

多孔钛酸钡陶瓷制备及其增强的压电灵敏性

在压电陶瓷中增加孔洞数量,可以有效改善陶瓷的静水压优值,提高其压电灵敏性.考虑到铅基压电陶瓷对环境和人体的危害,本文以糊精为造孔剂,采用传统固相烧结法制备无铅钛酸钡(BaTiO_3)多孔压电陶瓷.研究烧结温度(1250,1280,1300℃)和糊精含量(5%,10%,15%)对BaTiO_3陶瓷晶体结构、孔隙率以及孔形貌特征的影响,探索孔隙率与BaTiO_3陶瓷介电、压电、声阻抗以及静水压优值等性能之间的相关性.结果表明:所有多孔陶瓷表现出三维贯通的开气孔,尺寸约为1—7μm.烧结温度强烈影响BaTiO_3陶瓷的孔隙率,加入10%低沸点的糊精时,1250℃和1280℃烧结均获得孔隙率高达58%的多孔BaTiO_3陶瓷;然而1300℃烧结,陶瓷孔隙率急速下降到13%.1250℃烧结10%糊精含量的陶瓷表现出高的静水压优值(约8376×10~/(-15)Pa~(-1))和低的声阻抗(约2.84MRrayls(1Rayl=10Pa·s/m)).与1250℃相比,1280℃烧结的陶瓷晶粒之间的结合力明显增强,有利于提高陶瓷的力学强度.这些优异的性能预示着多孔钛酸钡陶瓷在传感器和水听器领域有着潜在的应用前景.     

热电材料PbTe1-xSex的高压制备及电学性能研究

 利用高温高压技术,制备了热电材料PbTe和PbSe的固溶体合金PbTe_1-xSe_x,在室温下对其结构及电学性质进行了研究。X射线衍射（XRD）测试结果表明：PbTe_1-xSe_x具有NaCl结构;晶格常数随着Se含量（x）的增加而减小;PbTe_1-xSe_x的电阻率和Seebeck系数的绝对值随x的增大而减小;功率因子随x的增大先增大而后减小,当x=0.1时功率因子最高,达到21.7 μW/(cm·K²),比相同条件下制备的PbTe高20%。     

Emerging Theory,Materials, and Screening Methods: New Opportunities for Promoting Thermoelectric Performance

High‐performance thermoelectric materials have attracted immense interest due to the capability of directly converting thermal energy into electrical energy. The correlation and inherent complexity between the thermoelectric parameters pose serious challenges to improving the materials’ thermoelectric performance. Herein, the emerging novel theories in the field of thermoelectrics are summarized, such as the coherent phonon, nanophononic metamaterial, rattling effect, topological phonon, and topological electron. The impacts of these new concepts on thermoelectric performance are then reviewed. Finally, a number of promising thermoelectric materials such as one‐dimensional nanowires, two‐dimensional layered materials, and nanomesh structures are discussed. The advanced understanding of thermal and electrical transport properties in thermoelectric materials is presented herein, providing new opportunities for improving thermoelectric performance.     

Thermoelectric Properties of the TlBiS<Subscript>2</Subscript>-PbS Alloys

High efficiency of thermoelectric conversion can be achieved by using materials with a high Seebeck coefficient, high electrical conductivity, and low thermal conductivity. Mass-difference-scattering of the phonons is one of the most effective way for reducing the thermal conductivity in bulk thermoelectric materials. Investigations of transport phenomena in (TlBiS₂)_1-x (2PbS)_x alloys system have shown that in solid solutions of the (A³B⁵C ₂ ⁶ )_1-x (2A⁴B⁶)_x type at cation substitution according to scheme 2A⁴⁽⁺²⁾ A ³⁽⁺¹⁾ + B⁵⁽⁺³⁾ occurs a strong decrease of the lattice thermal conductivity. In the vicinity of x = 0. 50 the lattice part of thermal conductivity of (TlBiS₂)_1-x (2PbS)_x alloys decreases down to 0. 26 W/mK, i. e., it approaches the theoretical minimum. As a result, the thermoelectric figure of merit for these alloys ( 25%) exceeds the respective value for lead sulfide at room temperature.     

高压合成AgSbTe2-Sb2Te3的热电性能研究

 利用高压方法,合成了富Sb₂Te₃的AgSbTe₂热电材料(AgSbTe₂)_1-x(Sb₂Te₃)_x (0≤x≤0.3),并对其结构和热电性质进行了研究。结果表明：(AgSbTe₂)_1-x(Sb₂Te₃)_x样品为近单相的AgSbTe₂材料;随着制备压力和Sb₂Te₃掺杂量的增加,(AgSbTe₂)_1-x(Sb₂Te₃)_x的电阻率大幅降低;Seebeck系数在高压作用下变小,而少量掺杂Sb₂Te₃却能提高Seebeck系数;在高压和微量掺杂Sb₂Te₃的共同作用下,AgSbTe₂的功率因子得到了提高;2.0 GPa高压下,制备的Ag_0.9Sb_1.1Te_2.1的品质因子达到0.466,接近Bi₂Te₃的品质因子。     

Thermoelectric properties of gated graphene ribbons in the ballistic regime

We investigate the thermoelectric properties of gated graphene ribbons in the ballistic transport limit using linear response theory and the Landauer formalism. The dependence of the electronic conductance, thermopower as well as electronic thermal conductance on both Fermi level and temperature are clarified and the validity of Wiedemann-Franz law is examined. The electronic part of thermoelectric figure of merit _ZTel${\mathit{ZT}}_{\mathit{el}}$ which gives an upper bound for the thermoelectric efficiency of the gated ribbons, is also calculated. It is shown that _ZTel${\mathit{ZT}}_{\mathit{el}}$ of wide and short gated ribbons is directly related to geometric aspect ratio of the graphene ribbon and for very short ribbons can exceed unity at room temperature. Our results could be useful in the design of efficient graphene-based thermoelectric devices.     

食品微生物对超高压处理的逆境响应

 超高压（High Hydrostatic Pressure,HHP）作为一种非热杀菌技术,在食品工业中有着很广泛的应用,与传统的热加工处理相比,在保持食品品质、杀菌、钝酶等方面都有其明显的优势。通过对国内外相关文献的分析,对HHP处理后处于亚致死状态食品微生物的细胞膜、遗传与结构物质、机体代谢等方面,以及大部分食品微生物在应对外界的多种刺激时而进行的普遍性调控机制的研究进行了总结,探讨了经过HHP处理后处于亚致死状态的食品微生物在逆境下存活的应激反应。     

Thermoelectric effect in a serial two-quantum-dot

We study the thermoelectric effect in a serial-coupled two quantum dots (QDs) device in the Coulomb blockade regime. The electrical conductance, the thermal conductance, the thermopower, and the thermoelectrical figure of merit are calculated by using the Green's function method. It is found that the energy levels of the two dots are split into a series of molecular states, where the electrical and the thermal conductances show resonance peaks. These peaks in the electrical conductance are eliminated by the increase of the temperature, while those in the thermal conductance are enhanced because of the bipolar effect. In quite high temperature regime, the figure of merit has two huge peaks with maximums exceeding 20 in the vicinity of the electron-hole symmetry point. The magnitude of the figure of merit will be suppressed for unequal dots' levels, but is enhanced by the asymmetry of the dot-lead coupling strengths.     

Geometry Optimization of Thermoelectric Modules: Deviation of Optimum Power Output and Conversion Efficiency

Besides the material research in the field of thermoelectrics, the way from a material to a functional thermoelectric (TE) module comes alongside additional challenges. Thus, comprehension and optimization of the properties and the design of a TE module are important tasks. In this work, different geometry optimization strategies to reach maximum power output or maximum conversion efficiency are applied and the resulting performances of various modules and respective materials are analyzed. A Bi₂Te₃-based module, a half-Heusler-based module, and an oxide-based module are characterized via FEM simulations. By this, a deviation of optimum power output and optimum conversion efficiency in dependence of the diversity of thermoelectric materials is found. Additionally, for all modules, the respective fluxes of entropy and charge as well as the corresponding fluxes of thermal and electrical energy within the thermolegs are shown. The full understanding and enhancement of the performance of a TE module may be further improved.