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Synthesis and characterization of nano-structured CoSb3 thermoelectric material
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
2009 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

In this project, nano powder of CoSb3 thermoelectric material was synthesized using chemical alloying novel co-precipitation method. This method involved co-precipitation of TE precursor compounds in controlled pH aqueous solutions followed by thermo-chemical treatments including calcination and reduction to produce nano-particulates of CoSb3. The nano powder was consolidated using rapid solid state spark plasma sintering (SPS) and the processing time was of the order of few minutes. On a result very high densities were achieved and grain growth was almost negligible.

Various batches of the CoSb3 nano powder were produced to achieve high purity, minimum particle size and compensate Sb evaporation during thermo-chemical reduction. For de-agglomeration, powder was grinded before and after calcination. Samples were characterized at each stage during synthesis using XRD and SEM (with EDX). Thermal gravimetric analysis (TGA) was done before thermochemical treatments to observe weight losses with heating the powder at high temperatures and other physiochemical changes. Thermal diffusivity of the samples was measured at room temperature using Laser Flash Apparatus (LFA) and heat capacity was measured using Differential Scanning Calorimetry (DSC).   Thermal conductivities are calculated using these thermal diffusivities, heat capacities and densities of the sintered pellets. Average grain size is measure using image size J software.

It was observed that powder purity and size is affected by batch size, reduction conditions like holding temperature and time.  During sintering with SPS; heating and cooling rates, sintering temperature, holding pressure and time were the main variables. Grain size and morphology was analyzed using SEM.

It was observed that larger the grain size higher will be the thermal diffusivity, which leads to increase in thermal conductivity. Hence, grain size has affected on thermal conductivity and also on TE performance.

Place, publisher, year, edition, pages
2009. , 73 p.
Keyword [en]
Thermoelectric CoSb3, Intermetallics, Spark Plasma Sintering, MS Thesis
National Category
Materials Engineering
URN: urn:nbn:se:kth:diva-10810ISRN: KTH/MSE- -09/31- -SE+CHEM/EXOAI: diva2:228012
QC 20100708Available from: 2010-07-08 Created: 2009-07-22 Last updated: 2010-07-08Bibliographically approved

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