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Simulation study of phononic crystal structures
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
2017 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Thermoelectric materials are important in today’s society with a variety of applications. The material properties that determinate the efficiency of a thermoelectric device are mostly constants. In order to develop more efficient thermoelectric devices new materials and solutions need to be made. Minimizing the thermal conductivity in thermoelectric materials is of great interest to make them more effective.

 

One effective way of lowering the thermal conductivity is to introduce holes in the lattice and create a phononic crystal. The main focus of this master thesis has been on how to place these holes and to optimize the geometry to minimize thermal conductivity. The method used in this report is based solely on simulations, which were done using Comsol Multiphysics 5.2a. The results are compared to already published results. Different geometries are tested to see how it affects the thermal conductivity and to optimize the phononic crystal. The Maxwell-Eucken model is also used to see how porosity affects the thermal conductivity and to analyze what the lowering in thermal conductivity depends on.

 

The result showed a substantial reduction in thermal conductivity when creating a phononic crystal compared to bulk silicon. The simulated reduction compared to bulk silicon is up to 98.5% when introducing holes in the lattice, while Maxwell-Eucken only predicted a 74% reduction due to porosity.

 

The conclusion is that by creating holes in a periodical pattern, phonon dispersion will occur, which lower the thermal conduction significantly.

Place, publisher, year, edition, pages
2017. , p. 47
Series
UPTEC Q, ISSN 1401-5773 ; 17003
National Category
Nano Technology
Identifiers
URN: urn:nbn:se:uu:diva-326118OAI: oai:DiVA.org:uu-326118DiVA, id: diva2:1118821
Educational program
Master Programme in Materials Engineering
Presentation
2017-03-03, Ångström 4006, Ångströmlaboratoriet, Lägerhyddsvägen. 1, Uppsala, 19:05 (English)
Supervisors
Examiners
Available from: 2017-07-03 Created: 2017-07-02 Last updated: 2017-07-03Bibliographically approved

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CiteExportLink to record
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