In order to improve the stability of Bi 2 Te 3 -based thermoelectric devices, we attempted to prepare a barrier layer via diffusion welding using Co powder as the barrier materials. The diffusion welding process was conducted at 674 K for a duration of 5 min. The optimal connection was achieved at the interfaces of Co/Bi 0.4 Sb 1.6 Te 3 and Co/Bi 2 Te 2.7 Se 0.3 . The results showed that the Co/Bi 0.4 Sb 1.6 Te 3 joint had diffusion thickness of 1.6 µm, contact resistivity of 0.83 µΩ cm 2 , and bonding strength of 4.86 MPa for the barrier layer. Similarly, the Co/Bi 2 Te 2.7 Se 0.3 joint had diffusion thickness of 1.6 µm, contact resistivity of 0.75 µΩ cm 2 , and bonding strength of 3.99 MPa for the barrier layer. The thermoelectric device fabricated through this process exhibited a hot–cold cycle number of 35,000, which was significantly higher than the device with a Ni-based barrier layer under similar experimental conditions. Thus, it indicates that Co is a promising material for the preparation of barrier layers in Bi 2 Te 3 -based thermoelectric devices.

Refrigeration using thermoelectric cooler (TEC) is a hotspot and frontier issue, but the forced heat dissipation apparatus poses problems that limit its application. In this paper, a thermoelectric refrigerator used under natural convection heat transfer conditions is presented, and numerical simulations and experimental analyses are performed. The maximum error between the simulation results and experimental results is 6.3%. The distribu-tions of the temperature and velocity field in the refrigerator chamber are obtained, and the influences of the operating current and the height of fins on the temperature are analyzed. The novel design is that the number of thermoelectric legs in a single TEC is reduced to five pairs to reduce the heat generated on the hot side during operation. The performance of TEC is improved by increasing the average heat dissipation area. The results show that the air temperature in the chamber is finally stabilized at 12.2 & DEG;C under the ambient temperature of 29 & DEG;C and input electric power of 10.8 W. The air temperature difference inside and outside the thermoelectric refrigerator increases from 16.8 & DEG;C to 19.5 & DEG;C with the fin's height increasing, but the coefficient of performance (COP) changes little.

Bismuth telluride-based thermoelectric devices are the only thermoelectric devices that are currently used in large-scale commercial applications. In actual production, nitric acid roughening solution corrodes them and generates a black substance on the surface that is difficult to remove. The exact composition of the black film is not known, which makes its removal even more difficult. In this study, it was observed by x-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM) that the black substance may be formed by the reaction of Sb 2 Te 3 in p -type bismuth telluride with nitric acid. Valence analysis by x-ray photoelectron spectrometry (XPS) showed the presence of Te in the black substance in the valence states of Te 4+ and Te 6+ , and Sb in the valence state of Sb 3+ . Fourier transform infrared spectrometry (FTIR) results showed the existence of four chemical bonds, including ν Te-O , ν Sb-O , ν Te-O-Te , and ν Te-O-Te , while ν N=O and δ N=O were also detected at 1361 cm −1 and 1039 cm −1 , respectively, indicating the presence of NO3 − in the black substance. Synthesizing the experimental phenomena and literature data, the composition of the black substance was presumed to be x TeO 2 -Sb 2 O 3 -HNO 3 (2 < x < 3), and the corresponding reaction chemical equation was given. This study provides an important reference for further optimization of the production process.

热电材料能够实现热能与电能的相互转换,是一种可以应用于余热回收及半导体制冷等相关领域的功能性材料.传统热电材料的发展目前已趋于成熟,但仍然面临着高昂的原料成本及较低的热电转换效率等问题.Mg3(Sb,Bi)2基热电材料自被发现以来就以其低成本的元素组成和作为Zintl相具备的本征低热导率受到广泛关注.其中n型传导样品由于高能带简并度的优势更是有着较高的塞贝克系数,相较于传统中低温热电材料具备更大的发展潜力.然而,较大的带隙使得Mg3(Sb,Bi)2基热电材料载流子浓度整体偏低,同时还存在着由Mg空位引起的热稳定性较差的问题.为此,在保证该材料低热导率的同时,研究者们尝试了不同的制备工艺,并通过组分优化和结构优化来不断改善其电输运性能及热稳定性.目前Mg3(Sb,Bi)2基热电材料的最大ZT值已经达到1.8以上,同时其器件化后的热电转换效率也可媲美于传统Bi2Te3基热电器件.本文总结了Mg3(Sb,Bi)2基热电材料的基础物理性能与制备方法,从不同的优化手段出发依次介绍了现阶段该材料的研究成果,并展望了其在未来可行的发展方向.