Silicon-based low-dimensional materials for thermal conductivity suppression: recent advances and new strategies to high thermoelectric efficiency

Abstract

Thermoelectric (TE) materials can convert any kind of heat into electricity through the Seebeck effect. Harvesting body heat and generating electricity by TE wearable devices can provide a convenient charge service for electrical equipment, even in the case of emergency or disaster. As a high-temperature excellent TE material, silicon also exhibits promising room temperature (RT) potential for wearable TE devices due to its safe and mature production line for the semiconductor industry. Aiming to search for solutions for reducing thermal conductivity (k), this review summarizes the low-dimensional strategies for reducing k based on nanostructural classification, thus enhancing zT at RT, and it also looks into the prospect of wearable application. Following in the footsteps of nanostack (NS), nanowire (NW), nanoporous (NP) and nanocomposite (NC) Sibased TE materials research, we found that the thermal conductivity has been well controlled and that harmonious regulation of the power factor (PF) with k will be the future direction. © 2020 The Japan Society of Applied Physics 14) and Mg 0.97 Zn 0.03 Ag 0.9 Sb 0.95 . 15) Nevertheless, two critical shortcomings limit their application on wearability. On the one hand, most of them are rare in lithosphere and toxic to the human body, which is not desirable in terms of their mass application on skin. On the other hand, the volume of convectional bulk materials cannot satisfy the demand of the increasing miniaturization of wearable terminals.

Dimensionality effects in high‐performance thermoelectric materials: Computational and experimental progress in energy harvesting applications

“…Furthermore, the microstructure could also intentionally control the behavior of the carrier and κ e , so that the total k can be reduced significantly. 32,56,60 3.3 | Designing the structure/geometry for TE module…”

Thermoelectric enhancement of p-type Si 80Ge 20 alloy via co-compositing of dual oxides: Respective regulation for power factor and thermal conductivity by β-Ga 2O 3 and SiO 2 aerogel powders

“…The sintered ingots were characterized by an X-ray diffractometer (D8 Advance, Bruker) with Cu Kα radiation, and the diffraction angle (2) was from 10° to 70° with a 0.02° step. The grain size of SiGe matrix (g) was calculated by Scherrer formula [3,4]: g  / ( cos ) K B   , where  (= 1.54056 Å) is the wavelength of Cu Kα radiation, B is the corrected full width at half maximum (FWHM),  is the satisfied angle of Bragg's principle, and K (≈ 0.9) is the Scherrer constant. The Raman shift evaluation was adopted via a Raman spectrometer (Lab HR Evolution, HORIBA).…”

“…However, the strong coupling correlation among them leads to the difficulty of simultaneous regulation, which restricts the upper limit of ZT value [1][2][3]. As the most extensively used semiconductors, Si-based materials exhibit promising potential in TE energy harvesting for miniaturized terminals [4][5][6][7] owing to the merits of chemical stable, environmentally friendly and abundant, as well as the ready availability of mature up-and down-stream industry chain. Although the face-centered cubic structure and good crystallinity of Si can result in excellent PF (~5000 μW•m −1 •K −2 at 300 K) [8], the intrinsically high l  caused overlarge  (~150 W•m −1 •K −1 ) [4] and yielded an extremely low ZT value (~0.15 at 1100 K) [8].…”

High thermoelectric power factors in sputter-deposited polycrystalline n-type BaSi2 films

“…10) Recently, TE materials have attracted renewed interest as power-generation sources for internet-of-things devices. Flexible TE materials, such as electrically conducting polymers, [11][12][13] hybrid composites, [14][15][16][17] and SiGe-based thin films, [18][19][20][21][22] have therefore attracted great interest. Semiconducting silicides, such as β-FeSi 2 , MnSi 1.7 , ReSi 1.75 , and SrSi 2 , have also been studied.…”