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A Comparative Study on the Thermoelectric Properties of Bismuth Chalcogenide Alloys Synthesized through Mechanochemical Alloying and Microwave-Assisted Solution Synthesis Routes
KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.ORCID iD: 0000-0002-5672-5727
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2020 (English)In: Frontiers in Materials, ISSN 2296-8016, Vol. 7, article id 569723Article in journal (Refereed) Published
Abstract [en]

The way a material is synthesized and processed has an immense effect on its microstructure, which in turn has a big impact on its transport properties. Here, we compare the thermoelectric (TE) properties of n- and p-type Bi2−xSbxTe3 (x: 0 and 1.5) materials synthesized through two different routes, specifically mechanochemical alloying (MA)—as a solid-state synthesis route—and microwave(MW)-assisted polyol synthesis—as a solution synthesis route. Reaction time is significantly reduced in the MW synthesis, leading to significantly lower energy consumption (i.e., higher energy efficiency) per batch than using the MA route. The resultant materials are compared for their crystallinity, phase purity, morphology, and microstructure. Spark plasma sintering was used to prepare pellets, and the resultant consolidates were evaluated for their transport properties. TE properties and microstructure of the specimens were investigated in relation to processing conditions and composition. MA samples formed fused structures (from 200 nm to several micrometers in size) composed of smaller particles. MW-synthesized materials exhibited hexagonal platelet morphology, high crystallinity, and phase purity. They also showed lower thermal conductivity, leading to a higher resultant TE figure-of-merit ZT. TE properties of Bi2−xSbxTe3 samples were studied on sintered cylindrical pellet samples, where the highest ZT values achieved were 1.04 (at 440 K) for MW-Bi2Te3 and 0.76 (at 523 K) for MW-Bi0.5Sb1.5Te3 samples, while MA-Bi2Te3 and MA-Bi0.5Sb1.5Te3 samples showed maximum ZT values of 0.74 (at 460 K) and 0.27 (at 300 K), respectively, as n- and p-type TE materials. The observed trend is much higher ZT values for MW samples, ascribed to their higher degree of texturing and nanostructured grains reducing the thermal conductivity, thus achieving a better overall performance, verifying the prospect to enhance ZT using MW-assisted solution synthesis approach.

Place, publisher, year, edition, pages
Frontiers Media S.A. , 2020. Vol. 7, article id 569723
Keywords [en]
electrical conductivity, mechanochemical alloying, microwave-assisted reaction, nanostructured thermoelectrics, Seebeck coefficient, thermoelectric figure-of-merit ZT, thermoelectric material
National Category
Materials Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-286572DOI: 10.3389/fmats.2020.569723ISI: 000582617400001Scopus ID: 2-s2.0-85092485061OAI: oai:DiVA.org:kth-286572DiVA, id: diva2:1509672
Note

QC 20201214

Available from: 2020-12-14 Created: 2020-12-14 Last updated: 2022-06-25Bibliographically approved
In thesis
1. Design, Synthesis and Characterization of Nanostructured Thermoelectric Materials
Open this publication in new window or tab >>Design, Synthesis and Characterization of Nanostructured Thermoelectric Materials
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The demand for energy is rapidly increasing, triggering more carbon emission and global warming. Alternative green energy sources are essential to secure the future generation from the effect of pollution and global warming. During the last few decades, thermoelectric (TE) materials gained interest, due to their capability of directly interconverting between heat and power, which can be used to convert waste heat to electricity.  One of the strategic TE adaptation approaches is to develop high efficiency TE materials from earth-abundant and non-toxic components. Not only the TE materials’ composition, but also the synthesis method, has to be environment friendly in order to create a green transition, with minimum adverse environmental impacts. Bottom-up microwave (MW) assisted synthesis routes, using water and polyalcohol as green solvents were demonstrated feasible to generate binary and ternary compositions of Bi2-xSbxTe3, which were effective in room temperature. A more earth abundant and environment friendly material composition, copper selenide (Cu2-XSe), effective at intermediate temperature regime (200-600 °C), was synthesized by MW-assisted thermolysis. The synthesized materials were characterized in terms of structure, microstructure, surface chemistry and TE transport properties, and showed significant improvement of TE performance compared to materials synthesized using conventional methods - mainly attributed to the preservation of nanostructure. Significant results have been achieved with improved material characteristics, while the time and the energy investment were substantially reduced. The developed processes with reduced time and carbon footprint offer excellent sustainable synthesis routes for large-scale synthesis of high-performance nanostructured TE materials as strategic energy materials. 

Abstract [sv]

Efterfrågan på energi ökar snabbt, vilket leder till mer koldioxidutsläpp och global uppvärmning. Alternativa gröna energikällor är nödvändigt för att skydda kommande generationer från effekterna av miljöföroreningar och global uppvärmning. Under de senaste decennierna har intresset för termoelektriska (TE) material ökat på grund av deras förmåga att direkt omvandla spillvärme till elektricitet. En av strategierna för TE-anpassning är att utveckla effektiva TE-material från i jordskorpan vanligt förekommande och ogiftig föreningar. Inte bara TE-materialens sammansättning, utan också hur de syntetiseras, bör vara miljövänligt för att skapa en grön övergång med minimal negativ miljöpåverkan. Grön mikrovågsassisterad botten upp syntes med vatten och sockeralkohol som lösningsmedel visades vara en möjlig metod för att generera binära och ternära föreningar av Bi2-xSbxTe3, vilka är effektiva vid rumstemperatur. Den i jordskorpan vanligt förekommande och miljövänliga kemiska föreningen kopparselenid (Cu2-XSe), vilken är effektivt vid mellantemperaturer (200-600°C), har syntetiseras genom MW-assisterad termolys. De syntetiserade materialen karakteriserades av deras struktur, mikrostruktur, ytkemi och termoelektriska transportegenskaper och visade betydande förbättringar av TE-prestanda jämfört med material syntetiserade med konventionella metoder, vilket primärt kan tillskrivas bevarandet av nanostrukturer. Betydande resultat har uppnåtts med överlägsna materialegenskaper, samtidigt som tid och energiåtgång reducerats avsevärt. Den utvecklade processen, med minskad tidsåtgång och koldioxidavtryck, erbjuder hållbara syntesvägar för storskalig syntes av effektiva TE-material med nanostrukturer för strategiska energimaterial.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2021. p. 75
Series
TRITA-SCI-FOU ; 2021:36
Keywords
Materials chemistry
National Category
Materials Chemistry
Research subject
Physics, Material and Nano Physics; Physics
Identifiers
urn:nbn:se:kth:diva-302383 (URN)978-91-8040-000-8 (ISBN)
Public defence
2021-10-15, BioX Library https://kth-se.zoom.us/j/63386528297, Albanova Universitetscentrum, Roslagstullsbacken 21, Stockholm och via zoom, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Energy AgencyEuropean Commission
Available from: 2021-09-22 Created: 2021-09-21 Last updated: 2022-06-25Bibliographically approved

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Hamawandi, BejanToprak, Muhammet

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