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Effect of Synthesis and Sintering Conditions on the Thermoelectric Properties of n-Doped Mg2Si
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2014 (English)In: Journal of Electronic Materials, ISSN 0361-5235, E-ISSN 1543-186X, Vol. 43, no 6, 2301-2306 p.Article in journal (Refereed) Published
Abstract [en]

Magnesium silicide (Mg2Si)-based alloys are promising candidates for thermoelectric (TE) energy conversion in the middle-high temperature range. The detrimental effect of the presence of MgO on the TE properties of Mg2Si based materials is widely known. For this reason, the conditions used for synthesis and sintering were optimized to limit oxygen contamination. The effect of Bi doping on the TE performance of dense Mg2Si materials was also investigated. Synthesis was performed by ball milling in an inert atmosphere starting from commercial Mg2Si powder and Bi powder. The samples were consolidated, by spark plasma sintering, to a density > 95%. The morphology, and the composition and crystal structure of samples were characterized by field-emission scanning electronic microscopy and x-ray diffraction, respectively. Moreover, determination of Seebeck coefficients and measurement of electrical and thermal conductivity were performed for all the samples. Mg2Si with 0.1 mol% Bi doping had a ZT value of 0.81, indicative of the potential of this method for fabrication of n-type bulk material with good TE performance.

Place, publisher, year, edition, pages
2014. Vol. 43, no 6, 2301-2306 p.
Keyword [en]
Magnesium silicide, thermoelectricity, SPS
National Category
Other Materials Engineering
URN: urn:nbn:se:kth:diva-147733DOI: 10.1007/s11664-014-3048-yISI: 000336372400125ScopusID: 2-s2.0-84901916139OAI: diva2:732817

QC 20140707

Available from: 2014-07-07 Created: 2014-07-03 Last updated: 2014-09-18Bibliographically approved
In thesis
1. Nano-EngineeredThermoelectric Materials for Waste Heat Recovery
Open this publication in new window or tab >>Nano-EngineeredThermoelectric Materials for Waste Heat Recovery
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Energy crisis and thermal management related issues have been highlighted in the modern century due to escalating demands for energy consumption and global warming from fossil fuels. Sustainable and alternative energy sources are an ever growing global concern. Thermoelectric (TE) materials have gained significant interest, due to effective solid-state energy conversion from waste heat to useful electrical energy and vice versa.   Clean, noise-free, and environment-friendly operation of TE devices has triggered great attention in viable technologies including automotive, military equipment, aerospace, and industries to scavenge waste heat into power. To date, conventional TE materials have shown limited energy conversion efficiency, i.e. TE Figure of Merit (ZT). However, the concept of nanostructuring and development of novel TE materials have opened excellent avenues to improve significantly the ZT values. Nano-engineered bulk TE materials allow effective phonon scattering at the high density of grain boundaries, which offer a way of lowering the thermal conductivity. 

Large-scale synthesis of TE nanomaterials is a challenge for the TE industry because of expensive fabrication processes involved. This thesis reports several nano-engineering approaches for fabricating large quantities of bulk nanostructured TE materials. We have developed bottom-up chemical synthesis routes, as well as top-down mechanical alloying methodologies, to produce highly pure, homogenous and highly crystalline TE nanomaterials. State of the art chalcogenide, iron antimonide, and silicide based TE materials have been investigated in this thesis. Chalcogenide are the best candidates for TE devices operating at temperature range up to 450 K.  Iron antimonide (FeSb2) have shown attractive performance below room temperature. Earth abundant and environment friendly, silicide based materials have better ZT performance in the range of 600-900 K.  Spark plasma sintering (SPS) was utilized to preserve the nanostructuring and to achieve the highest compaction density. Comprehensive physiochemical characterizations were performed on as-prepared and SPS compacted samples. Detailed TE evaluation of the fabricated materials showed significant improvement in ZT for all categories of TE materials.

Place, publisher, year, edition, pages
Stockholm 2014: KTH Royal Institute of Technology, 2014. xi, 52 p.
TRITA-ICT/MAP AVH, ISSN 1653-7610 ; 2014:12
National Category
Materials Chemistry
urn:nbn:se:kth:diva-151363 (URN)978-91-7595-210-9 (ISBN)
Public defence
2014-10-03, SAl B, Electrum 229, Isafajordsgatan 22, Kista, 14:00 (English)
Swedish Energy Agency, 36656-1EU, FP7, Seventh Framework Programme, 263167Swedish Foundation for Strategic Research , EM11-0002EU, FP7, Seventh Framework Programme, 228882

QC 20140918

Available from: 2014-09-18 Created: 2014-09-18 Last updated: 2014-09-18Bibliographically approved

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Saleemi, MohsinToprak, Muhammet
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