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On the chemical synthesis route to bulk-scale skutterudite materials
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.ORCID iD: 0000-0003-0855-5265
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics. Stockholm University, Sweden.ORCID iD: 0000-0001-5380-975X
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2016 (English)In: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 42, no 4, 5312-5318 p.Article in journal (Refereed) PublishedText
Abstract [en]

In this article an alternative high yield route for the synthesis of CoSb3-based unfilled skutterudites is presented. Using low-melting temperature salts of the constituents, melting and mixing them homogeneously in a hydrophobic liquid with postprocessing of the powders we achieve a more intimately mixed alloy compared to the conventional melting and metallurgical processes. The proposed method consists of a fast and low-temperature processing step followed by a thermochemical post-processing step, compared to the conventional methods of fabricating skutterudites, which require high temperatures and long processing times. Several structural characterization techniques were used to assess the mechanism of synthesis, verify the purity of the material as well as the reproducibility of the process. Detailed analysis and results are presented in support of the proposed process. Additionally, compaction of the powders with SPS technique provided a safe route to maintaining the nanopowder size and achieving low thermal conductivity (3 W/mK). The proposed method can easily be scaled up and adopted by the industry.

Place, publisher, year, edition, pages
Elsevier, 2016. Vol. 42, no 4, 5312-5318 p.
Keyword [en]
Thermal conductivity, Thermoelectric, Skutterudite, TGA-FTIR
National Category
URN: urn:nbn:se:kth:diva-183303DOI: 10.1016/j.ceramint.2015.12.061ISI: 000369460500088ScopusID: 2-s2.0-84955655812OAI: diva2:910665

QC 20160309

Available from: 2016-03-09 Created: 2016-03-07 Last updated: 2016-05-03Bibliographically approved
In thesis
1. Nanostructured Bulk Thermoelectrics: Scalable Fabrication Routes, Processing and Evaluation
Open this publication in new window or tab >>Nanostructured Bulk Thermoelectrics: Scalable Fabrication Routes, Processing and Evaluation
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Current fossil fuel based energy sources have a huge shortcoming when one discusses their efficiency. The conversion efficiency of fossil fuel-based technologies is less than 40% in best cases. Therefore, until the renewable energy section is mature enough to handle all the energy demand one has to research and develop the technologies available to harvest the energy from the waste heat generated in fossil fuel-based supply sources. One of these emerging technologies is the use of thermoelectric (TE) devices to achieve this goal, which are solid-state devices capable of directly interconverting between heat and electrical energy. In the past decade there has been a significant scientific and financial investment within the field to enhance their properties and result in time/energy efficient fabrication processes of TE materials and devices for a more sustainable environment.

In this thesis with use of chemical synthesis routes for nanostructured bulk thermoelectric materials iron antimonide (FeSb2), skutterudites (based on general formula of RzMxCo1-xSb3-yNy) and copper selenide (Cu2Se) are developed. These materials are promising candidates for use in thermoelectric generators (TEG) or for sensing applications. Using chemical synthesis routes such as chemical co-precipitation, salt melting in marginal solvents and thermolysis, fabrication of these TE materials with good performance can be performed with high degree of reproducibility, in a much shorter time, and easily scalable manner for industrial processes. The TE figure of merit ZT of these materials is comparable to, or better than their conventional method counterparts to ensure the applicability of these processes in industrial scale.

Finally, through thorough investigation, optimized consolidation parameters were generated for compaction of each family of materials using Spark Plasma Sintering technique (SPS). As each family of TE nanomaterial investigated in this thesis had little to no prior consolidation literature available, specific parameters had to be studied and generated. The aim of studies on compaction parameters were to focus on preservation of the nanostructured features of the powder while reaching a high compaction density to have positive effects on the materials TE figure of merit.

Abstract [sv]

Dagens fossilbränslebaserade energikällor har en enorm brist gällande effektivitet. Effektiviteten av fossilbränslebaserade teknologiers omvandling är mindre än 40 % i bästa fall. Därför tills förnybar energi är mogen nog att hantera alla energibehov, måste man forska och utveckla teknik för att skörda energi från spillvärme i fossilbränslebaserade försörjningskällor. En av dessa nya tekniker är tillämpning av termoelektriska (TE) material för att uppnå målet. Nämnde material är Soldi-State materialer som kan transformera mellan värme och elektrisk energi. Under det senaste decenniet har det pågått en stor vetenskaplig och ekonomisk investering inom området för att förbättra termoelektriska materials egenskaper. Dessutom ville man ta fram tid/energieffektiva TE material och komponenter för en mer hållbar miljö.

I denna avhandling utvecklades och producerades termoelektriska material såsom järn antimonid (FeSb2), skutterudit (baserat på allmänna formeln RzMxCo1-xSb3-YNY) och koppar selenid (Cu2Se) med hjälp av kemiska syntesmetoder. Genom att Använda kemiska syntesmetoder som kemisk samutfällning, salt smältning i marginella lösningsmedel och termolys, kan material med hög grad av reproducerbarhet och ställbar för industriella processer tillverkas.   Termoelektrisk omvandling effektivitet hos uppnådde material är betydligt högre än resultat av andra studier. I och med detta kan man säga att materialet kan användas inom industri.

Slutligen, genom en grundlig undersökning optimerades packningsparametrar som genererades för packning av varje materialgrupp med hjälp av Spark Plasma Sintring teknik (SPS). Eftersom ingen relevant studie finns för varje grupp av termoelektriska nanomaterial som undersökts i denna avhandling, studerades och genererades dessa specifika parametrar. Syftet med studien är att fokusera på bevarande av nanostrukturerade egenskaperna hos pulvret och att samtidigt nå en hög packningstäthet för att ha positiva effekter på materialens termoelektriska omvandlingseffektivitet.

Place, publisher, year, edition, pages
Stockholm, Sweden: KTH Royal Institute of Technology, 2016. x, 34 p.
TRITA-ICT, 2016:10
Thermoelectric, Iron antimonide (FeSb2) Skutterudite, Copper Selenide (Cu2Se), Spark Plasma Sintering (SPS), nanomaterial
National Category
Condensed Matter Physics
Research subject
Materials Science and Engineering; Energy Technology
urn:nbn:se:kth:diva-186124 (URN)978-91-7595-945-0 (ISBN)
Public defence
2016-05-27, Sal C, Isafjordsgatan 22, Kista, 10:00 (English)
Swedish Foundation for Strategic Research , EM11‐0002EU, FP7, Seventh Framework Programme, 263167

QC 20160503

Available from: 2016-05-03 Created: 2016-05-02 Last updated: 2016-05-10Bibliographically approved

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