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Structure and Properties of Advanced Thermoelectric Materials and Devices

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Smart Materials".

Deadline for manuscript submissions: closed (20 January 2024) | Viewed by 4458

Special Issue Editor


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Guest Editor
School of Materials Science and Engineering, University of Science Technology Beijing, Beijing, China
Interests: thermoelectric materials and devices

Special Issue Information

Dear Colleagues,

With the prosperous development of the global economy, the increasing energy crunch and environmental pollution are significant challenges around the world. It is thus an urgent problem for us to develop new, green, and environmentally friendly renewable energy conversion materials and technologies. Thermal energy and electric energy are the most important forms of energy in our social life. Electric energy is one of the most convenient forms for energy transmission and use. Thermoelectric materials and devices can make use of many kinds of thermal energy, such as nuclear heat, solar heat, geothermal heat, ocean heat, and various waste heats to generate power. Because of their unique advantages, including their simple structure, strength and durability, lack of moving parts, portability, mobility, lack of need for maintenance, stable performance, long life (more than 30 years), lack of pollution, ultra-quiet nature, and so on, thermoelectric generators are an important or even the only choice for many key applications. The only drawback is low thermoelectric conversion efficiency. Therefore, improving conversion efficiency has become a research hotspot that has received extensive attention by scientists at home and abroad.

After more than 200 years of research and development, scientists have proposed many theories and implementation schemes to improve the thermoelectric properties of materials and devices, such as band regulation (increasing the band degeneracy Nv, introducing resonance levels near the Fermi level to increase the density of states, changing the gap width, introducing an impurity level to improve carrier concentration and reduce lattice thermal conductivity), reduction in lattice thermal conductivity, low-dimensional quantum structure or nanocomposite structure, etc. However, the research results are not very satisfactory, and the highest dimensionless thermoelectric optimum value ZTmax of the applied materials has been maintained at about 1. Despite this, some new structures and compositions of thermoelectric materials and devices with high thermoelectric properties have been reported in recent years. In line with the research policy of connecting the preceding and the following, this Special Issue focuses on this topic and invites both reviews and research papers.

This Special Issue aims to cover recent progress and new developments in the relationships between the structure and properties of advanced thermoelectric materials and devices. All aspects related to new structures, new principles, new concepts, new materials, new methods, new processes, physical and numerical simulation, and new applications in the field of thermoelectric materials and devices are covered. Review articles which describe the current state of the art are also welcomed.

Prof. Dr. Guiying Xu
Guest Editor

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Keywords

  • structure
  • preparation
  • performance
  • thermoelectric
  • materials
  • devices

Published Papers (5 papers)

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Research

16 pages, 6204 KiB  
Article
Crucial Role of Ni Point Defects and Sb Doping for Tailoring the Thermoelectric Properties of ZrNiSn Half-Heusler Alloy: An Ab Initio Study
by Eleonora Ascrizzi, Chiara Ribaldone and Silvia Casassa
Materials 2024, 17(5), 1061; https://doi.org/10.3390/ma17051061 - 25 Feb 2024
Viewed by 661
Abstract
In the wide group of thermoelectric compounds, the half-Heusler ZrNiSn alloy is one of the most promising materials thanks to its thermal stability and narrow band gap, which open it to the possibility of mid-temperature applications. A large variety of defects and doping [...] Read more.
In the wide group of thermoelectric compounds, the half-Heusler ZrNiSn alloy is one of the most promising materials thanks to its thermal stability and narrow band gap, which open it to the possibility of mid-temperature applications. A large variety of defects and doping can be introduced in the ZrNiSn crystalline structure, thus allowing researchers to tune the electronic band structure and enhance the thermoelectric performance. Within this picture, theoretical studies of the electronic properties of perfect and defective ZrNiSn structures can help with the comprehension of the relation between the topology of defects and the thermoelectric features. In this work, a half-Heusler ZrNiSn alloy is studied using different defective models by means of an accurate Density Functional Theory supercell approach. In particular, we decided to model the most common defects related to Ni, which are certainly present in the experimental samples, i.e., interstitial and antisite Ni and a substitutional defect consisting of the replacement of Sn with Sb atoms using concentrations of 3% and 6%. First of all, a comprehensive characterization of the one-electron properties is performed in order to gain deeper insight into the relationship between structural, topological and electronic properties. Then, the effects of the modeled defects on the band structure are analyzed, with particular attention paid to the region between the valence and the conduction bands, where the defective models introduce in-gap states with respect to the perfect ZrNiSn crystal. Finally, the electronic transport properties of perfect and defective structures are computed using semi-classical approximation in the framework of the Boltzmann transport theory as implemented in the Crystal code. The dependence obtained of the Seebeck coefficient and the power factor on the temperature and the carrier concentration shows reasonable agreement with respect to the experimental counterpart, allowing possible rationalization of the effect of the modeled defects on the thermoelectric performance of the synthesized samples. As a general conclusion, defect-free ZrNiSn crystal appears to be the best candidate for thermoelectric applications when compared to interstitial and antisite Ni defective models, and substitutional defects of Sn with Sb atoms (using concentrations of 3% and 6%) do not appreciably improve electronic transport properties. Full article
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12 pages, 4792 KiB  
Article
Largely Enhanced Thermoelectric Power Factor of Flexible Cu2−xS Film by Doping Mn
by Xinru Zuo, Xiaowen Han, Yiming Lu, Ying Liu, Zixing Wang, Jiajia Li and Kefeng Cai
Materials 2023, 16(22), 7159; https://doi.org/10.3390/ma16227159 - 14 Nov 2023
Viewed by 849
Abstract
Copper-sulfide-based materials have attracted noteworthy attention as thermoelectric materials due to rich elemental reserves, non-toxicity, low thermal conductivity, and adjustable electrical properties. However, research on the flexible thermoelectrics of copper sulfide has not yet been reported. In this work, we developed a facile [...] Read more.
Copper-sulfide-based materials have attracted noteworthy attention as thermoelectric materials due to rich elemental reserves, non-toxicity, low thermal conductivity, and adjustable electrical properties. However, research on the flexible thermoelectrics of copper sulfide has not yet been reported. In this work, we developed a facile method to prepare flexible Mn-doped Cu2−xS films on nylon membranes. First, nano to submicron powders with nominal compositions of Cu2−xMnyS (y = 0, 0.01, 0.03, 0.05, 0.07) were synthesized by a hydrothermal method. Then, the powders were vacuum-filtrated on nylon membranes and finally hot-pressed. Phase composition and microstructure analysis revealed that the films contained both Cu2S and Cu1.96S, and the size of the grains was ~20–300 nm. By Mn doping, there was an increase in carrier concentration and mobility, and ultimately, the electrical properties of Cu2−xS were improved. Eventually, the Cu2−xMn0.05S film showed a maximum power factor of 113.3 μW m−1 K−2 and good flexibility at room temperature. Moreover, an assembled four-leg flexible thermoelectric generator produced a maximum power of 249.48 nW (corresponding power density ~1.23 W m−2) at a temperature difference of 30.1 K, and had good potential for powering low-power-consumption wearable electronics. Full article
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19 pages, 5031 KiB  
Article
Innovative Design of Bismuth-Telluride-Based Thermoelectric Transistors
by Hao Deng, Bohang Nan and Guiying Xu
Materials 2023, 16(16), 5536; https://doi.org/10.3390/ma16165536 - 9 Aug 2023
Cited by 1 | Viewed by 707
Abstract
Conventional thermoelectric generators, predominantly based on the π-type structure, are severely limited in their applications due to the relatively low conversion efficiency. In response to the challenge, in this work, a Bi2Te3-based thermoelectric transistor driven by laser illumination is [...] Read more.
Conventional thermoelectric generators, predominantly based on the π-type structure, are severely limited in their applications due to the relatively low conversion efficiency. In response to the challenge, in this work, a Bi2Te3-based thermoelectric transistor driven by laser illumination is demonstrated. Under laser illumination, a temperature difference of 46.7 °C is produced between the two ends of the transistor structure. Further, the hole concentrations in each region redistribute and the built-in voltages decrease due to the temperature difference, leading to the formation of the transistor circuit. Additionally, the operation condition of the thermoelectric transistor is presented. The calculation results demonstrate that the maximum output power of such a designed thermoelectric transistor is 0.7093 μW. Full article
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16 pages, 771 KiB  
Article
High-Throughput Screening of High-Performance Thermoelectric Materials with Gibbs Free Energy and Electronegativity
by Guiying Xu, Jiakai Xin, Hao Deng, Ran Shi, Guangbing Zhang and Ping Zou
Materials 2023, 16(15), 5399; https://doi.org/10.3390/ma16155399 - 1 Aug 2023
Cited by 1 | Viewed by 958
Abstract
Thermoelectric (TE) materials are an important class of energy materials that can directly convert thermal energy into electrical energy. Screening high-performance thermoelectric materials and improving their TE properties are important goals of TE materials research. Based on the objective relationship among the molar [...] Read more.
Thermoelectric (TE) materials are an important class of energy materials that can directly convert thermal energy into electrical energy. Screening high-performance thermoelectric materials and improving their TE properties are important goals of TE materials research. Based on the objective relationship among the molar Gibbs free energy (Gm), the chemical potential, the Fermi level, the electronegativity (X) and the TE property of a material, a new method for screening TE materials with high throughput is proposed. This method requires no experiments and no first principle or Ab initio calculation. It only needs to find or calculate the molar Gibbs free energy and electronegativity of the material. Here, by calculating a variety of typical and atypical TE materials, it is found that the molar Gibbs free energy of Bi2Te3 and Sb2Te3 from 298 to 600 K (Gm = −130.20~−248.82 kJ/mol) and the electronegativity of Bi2Te3 and Sb2Te3 and PbTe (X = 1.80~2.21) can be used as criteria to judge the potential of materials to become high-performance TE materials. For good TE compounds, Gm and X are required to meet the corresponding standards at the same time. By taking Gm = −130.20~−248.82 kJ/mol and X = 1.80~2.21 as screening criteria for high performance TE materials, it is found that the Gm and X of all 15 typical TE materials and 9 widely studied TE materials meet the requirement very well, except for the X of Mg2Si, and 64 pure substances are screened as potential TE materials from 102 atypical TE materials. In addition, with reference to their electronegativity, 44 pure substances are selected directly from a thermochemical data book as potential high-performance TE materials. A particular finding is that several carbides, such as Be2C, CaC2, BaC2, SmC2, TaC and NbC, may have certain TE properties. Because the Gm and X of pure substances can be easily found in thermochemical data books and calculated using the X of pure elements, respectively, the Gm and X of materials can be used as good high-throughput screening criteria for predicting TE properties. Full article
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12 pages, 3665 KiB  
Article
Preparation and Laser-Induced Thermoelectric Voltage Effect of Bi2Sr2Co2Oy Thin Films Grown on Al2O3 (0001) Substrate
by Ping Zou, Dan Lv, Hui Zhang and Zhidong Li
Materials 2023, 16(14), 5165; https://doi.org/10.3390/ma16145165 - 22 Jul 2023
Cited by 2 | Viewed by 677
Abstract
Bi2Sr2Co2Oy thin films were grown on 10° vicinal-cut Al2O3 (0001) single crystalline substrates by pulsed laser-deposition techniques with in situ annealing, post-annealing and non-annealing process, respectively. The pure phase Bi2Sr2 [...] Read more.
Bi2Sr2Co2Oy thin films were grown on 10° vicinal-cut Al2O3 (0001) single crystalline substrates by pulsed laser-deposition techniques with in situ annealing, post-annealing and non-annealing process, respectively. The pure phase Bi2Sr2Co2Oy thin film was obtained with a non-annealing process. The result of X-ray diffraction showed that Bi2Sr2Co2Oy thin film was obviously c-axis preferred orientation. The laser-induced thermoelectric voltage signals were detected in Bi2Sr2Co2Oy thin films, which originated from the anisotropy of the Seebeck coefficient. The maximum peak value of laser-induced thermoelectric voltage was strong and could reach as large as 0.44 V and the response time was 1.07 μs when the deposition time was 6 min. Furthermore, the peak voltage enhanced linearly with the single-pulse laser energy. These characteristics demonstrate that Bi2Sr2Co2Oy thin film is also an excellent choice for laser energy/power detectors. Full article
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