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Temperature Dependent Structure Stability Studies on Thermoelectric Yb0.025Fe0.3Co0.7Sb3
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM. (Material & NanoPhysics)ORCID iD: 0000-0003-0855-5265
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.ORCID iD: 0000-0001-5380-975X
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2015 (English)In: Materials Research Society Proceeding / [ed] S.R. Bishop , D. Cahen , R. Chen , E. Fabbri , F.C. Fonseca and D. Ginley, Materials Research Society , 2015, Vol. 1735Conference paper (Refereed)
Abstract [en]

Depending on their application temperature thermoelectric (TE) materials are classified in three main categories; as low (up to 250°C), intermediate (up to 550°C) and high (above 600°C) temperature. Currently, Skutterudites (CoSb3) based materials have shown promising results in the intermediate temperature range (300-500°C). This family of material is highly suitable for automotive, marine transportation and industrial power generation applications to recover the waste heat from the exhaust and generate electricity. Conventional TE modules need p- and n-type semiconductor materials and for the skutterudite family, iron (Fe) has proven to be among the best candidates for the substitution of cobalt sites. Additionally, rare earths are introduced as rattlers in the crystal cages of the skutterudite to decrease the thermal conductivity, thus improving the figure of merit ZT of the TE material. For practical application for device fabrication, stability of these materials is of great importance. Compositional stability is being addressed as the material decomposes above certain temperature. Temperature dependent x-ray diffraction study was performed on Fe substituted, Yb-filled skutterudites, using Beam Line I711 at MAX LAB, to observe the crystal structure as a function of temperature. Diffraction patterns were collected from room temperature up to 500°C by utilizing Huber furnace. The results show success in filling process showing almost 80% reduction of the thermal conductivity from bulk. Additionally the thermal expansion coefficient value was within the average value for skutterudites which proves practical application of this powder for industrial applications.

Place, publisher, year, edition, pages
Materials Research Society , 2015. Vol. 1735
Keyword [en]
thermoelectric, nanostructure, thermal conductivity
National Category
Materials Engineering
Research subject
Energy Technology
URN: urn:nbn:se:kth:diva-176849DOI: 10.1557/opl.2015.308OAI: diva2:868338
2014 MRS Fall Meeting
Swedish Research Council, VR-SRL 2013-6780Swedish Foundation for Strategic Research , EM11-0002

QC 20151201

Available from: 2015-11-10 Created: 2015-11-10 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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