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[National Science Review--Cooler, Stronger, Smaller- Improving Thermoelectric Cooling.pdf](https://mdr.nims.go.jp/filesets/a0c9a2a0-1f17-4eba-93f0-69c540ef191c/download)

## Creator

[Nagendra Singh Chauhan](https://orcid.org/0000-0003-2579-6642), [Takao Mori](https://orcid.org/0000-0003-2682-1846)

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[Creative Commons BY Attribution 4.0 International](https://creativecommons.org/licenses/by/4.0/)

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[Cooler, stronger, smaller: improving thermoelectric cooling](https://mdr.nims.go.jp/datasets/ce8deb02-203e-4ad3-918b-103cd6e5c262)

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Cooler, stronger, smaller: improving thermoelectric coolingRESEARCH HIGHLIGHT National Science Review 12: nwae445, 2025 https://doi.org/10.1093/nsr/nwae445Advance access publication 4 December 2024 MATERIALS SCIENCE Cooler, stronger, smaller: improving thermoelectric cooling Nagendra Singh Chauhan 1 and Takao Mori 1 , 2 , ∗Bltib[itBx50 μm(b)Enabling miniaturization of modulesyzF & SiCe (Sample 4)Reported worksFlexural strengthCompressive strengthZMMS-PASHPS-BM-SPSTIFSCompressive strength, σc (MPa)2752502252001751501251007550250[5]Other TE materialsmodulesB2Te3-basedmodules350Th (K)Sun et al.Li et al.Li et al.Kim et al.Zhu et al.Xing et al.Cho et al.Liu et al.Lu et al.Liu et al.Yang et al.Parashchuket al.Ying et al.Qin et al.Xie et al.Liu et al.Qin et al.Zhuang et al. [5]HighmechanicalstrengthHigh cooling efficiencyF r (Bi,Sb)2 Te3 -based nanocomposites, designed to enhance (a) mechanical strength and (c) cooling ef- fi g (b) micro cuboid pillar arrays, highlighting advancements in solid-state refrigeration. Adapted with pefficiency ( η) and enhance the per- formance (coefficient of performance, COP) of cooling systems, reigning as the present champion material in commer- cial Peltier modules or thermoelectric coolers (TECs). Compact and reliable, TECs leverage the Peltier effect for pre- cise micro-cooling in compact spaces, making them ideal for optoelectronics, wearable tech, and medical devices. The need for such TECs and relatively low temperature energy harvesting is inten- sifying, and also stimulating research into novel replacement materials such as Mg3 (Sb,Bi)2 [4 ]. New research on Bi2 Te3 by Zhuang et al. [5 ], published in National Science Review , reveals a multi-step process involving annealing, ©CwDownloaded from https://academic.oup.com/nsr/article/12/1/nwae445/7916659 by NATIONAL INSTITUTE FOR MATERIALS SCIENCE user on 22 January 2025ismuth telluride (Bi2 Te3 ) alloys have ong been the backbone of thermoelec- ric technology, driving breakthroughs n solid-state refrigeration and possi- le power generation for over 60 years 1 –3 ]. With continuous advancements n both n -type (Bi2 Te3–x Sex ) and p - ype (Bix Sb2–x Te3 ) based compositions, i2 Te3 continues to elevate thermal WithoutA-HF(Sample 1)HFA-HF(Sample 2)A-HF & SiC(Sample 3)A-H& TFlexural strength, σb (MPa)2001751501251007550250Zhuang et al. 100806040300 325ΔT max (K)(a)(c)igure 1. Schematic of process optimization fociency to fabricate micro-Peltier coolers havinermission from Ref. [5 ]. The Author(s) 2024. Published byOxfordUniversity Press on behalf of China Science Publishing &Media Ltd. This is anOpen Access article distributed under the terms of the Creativeommons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original ork is properly cited. https://doi.org/10.1093/nsr/nwae445https://orcid.org/0000-0003-2579-6642https://orcid.org/0000-0003-2682-1846https://creativecommons.org/licenses/by/4.0/Natl Sci Rev, 2025, Vol. 12, nwae445htmaotltfstSadypfp(rscmssyoie(aDndposdsm[sesdndce[aSncpsc2smizmfrcsmfoircepmppdFT(CNT1NMST∗ER   1©CwDownloaded from https://academic.oup.com/nsr/article/12/1/nwae445/7916659 by NATIONAL INSTITUTE FOR MATERIALS SCIENCE user on 22 January 2ot-forging and composition design o enhance both thermoelectric and echanical performance of (Bi,Sb)2 Te3 lloys by engineering atomic defects and ptimizing nano-/micro-structures. (Bi,Sb)2 Te3 alloys are inherently brit- le due to strong ionic/covalent bonding, ow fracture strain, and anisotropic tex- uring, which boosts thermoelectric per- ormance but compromises mechanical trength, creating a strength-performance rade-off [6 –8 ]. The processed (Bi, b)2 Te3 nanocomposites show remark- ble mechanical enhancement, improved ensity and refined microstructures, ielding a peak zT of ∼1.5 with excellent rocessability, ideal for micro-TECs abrication. Notably, flexural and com- ressive strengths increase by up to 50%  ∼140 MPa) and 40% ( ∼224 MPa), espectively, in optimized samples—urpassing typical values obtained from onventional methods, involving ball i l ling, melt spinning and spark plasma intering as shown in Fig. 1 a. For in- tance, zone melting methods typically ield flexural and compressive strengths f only ∼10 MPa. Superior mechan- cal strength and high processability nables the fabrication of ultra-small  ∼3 0 × 3 0 μm2 ) micro cuboid pi l lar rrays for TECs presented in Fig. 1 b. iced pi l lars, paired with commercial  -type Bi2 Te3 legs, support scalable pro- uction of micro-PCs with outstanding erformance, achieving peak cooling f �Tmax ∼ 89.3 K and a COP ∼ 6.6, urpassing conventional Bi2 Te3 -based evices as displayed in Fig. 1 c. Hot forging creates dense, high- trength microstructures with minimal The Author(s) 2024. Published by Oxford University Press onommons Attribution License ( https://creativecommons.org/lork is properly cited. icropores and increased dislocations 8 ,9 ], while nano SiC particles enhance trength through strain and dispersion ffects, lowering thermal conductivity imultaneously. Adding excess Te re- uces vacancy concentration by creating anoscale lattice distortions and dense islocations, which improves carrier oncentration and mobility, thereby nhancing thermoelectric performance 1 –3 ]. The process optimizations of nnealing-hot forging process and nano iC-Te incorporation in (Bi,Sb)2 Te3 anocomposites enhances electrical onductivity, weighted mobility, and ower factor, boosting zT through ynergistically reduced lattice thermal onductivity, realizing η ∼7.5% at �T = 25 K. In summary, Zhuang et al . [5 ] demon- trates scalable (Bi,Sb)2 Te3 micro-TECs, easuring just 2 × 2 mm2 to achieve mpressive cooling ( �Tmax up to 89.3 K, T ∼1.50 at a Th ∼ 348 K) and enhanced echanical strength, which is promising or efficient micro-TECs in solid-state efrigeration. Seiko previously fabri- ated thermoelectric watches utilizing ub-mi l limeter sized Bi2 Te3 -based ther- oelectric generator (TEG) legs [10 ]. As urther general issues for development f various thermoelectric applications, nexpensive thermoelectric module fab- ication methods remain an important hallenge. Advancements in thermo- lectric cooling towards more efficient, recise, compact and intelligent ther- al management solutions, is poised to lay a vital role in next-generation high- erformance micro- and opto-electronic evices.  behalf of China Science Publishing & Media Ltd. This is an Opeicenses/by/4.0/), which permits unrestricted reuse, distributioPage 2 of 2UNDING his work was supported by the JST Mirai Program JPMJMI19A1). onflict of Interest Statement. None declared. agendra Singh Chauhan 1 and akao Mori 1 , 2 , ∗ Research Center for Materials anoarchitectonics (MANA), National Institute for aterials Science (NIMS), Japan and 2 Graduate chool of Pure and Applied Sciences, University of sukuba, Japan Corresponding author. -mail: mori.takao@nims.go.jpEFERENCES 1. Hendricks T, Caillat T, Mori T. Energies 2022; 15 : 7307. 2. Scherrer H and Scherrer S. CRC Handbook of Ther- moelectrics . Boca Raton: CRC Press, 2018, 211–38. 3. Xu C, Shang H, Liang Z et al. Thermoelectric Mi- cro/Nano Generators, Volume 2: Challenges and Prospects . New York: Wiley, 2023. 4. Bano S, Chetty R, Babu J et al. Device 2024; 2 :100408. 5. Zhuang H-L, Cai B, Pan Y et al. Natl Sci Rev 2024; 11 : nwae329. 6. Lu Y, Zhou Y, Wang W et al. Nat Nanotechnol2023; 18 : 1281–8. 7. Zhou J, Feng J, Li H et al. Small 2023; 19 :2300654. 8. Mori T. Nat Nanotechnol 2023; 18 : 1255–6. 9. Zhu Y-K, Jin Y, Zhu J et al. Adv Sci 2023; 10 :2206395. 0. Qi Y and McAlpine MC. Energy Environ Sci 2010; 3 : 1275–85. n Access article distributed under the terms of the Creative n, and reproduction in any medium, provided the original 025https://orcid.org/0000-0003-2579-6642https://orcid.org/0000-0003-2682-1846mailto:mori.takao@nims.go.jphttp://dx.doi.org/10.3390/en15197307http://dx.doi.org/10.1016/j.device.2024.100408http://dx.doi.org/10.1093/nsr/nwae329http://dx.doi.org/10.1038/s41565-023-01457-5http://dx.doi.org/10.1002/smll.202300654http://dx.doi.org/10.1038/s41565-023-01464-6http://dx.doi.org/10.1002/advs.202206395http://dx.doi.org/10.1039/c0ee00137fhttps://creativecommons.org/licenses/by/4.0/ FUNDING REFERENCES