With decarbonisation, global increase of inflation, rising energy cost, etc., need for energy with low environmental impact have considerably shot up. Among all available technologies, thermoelectric generators (TEG) are solid-state devices converting heat into electricity thanks to Seebeck effect. TEGs present several advantages such as having no moving part, completely silent (unlike internal combustion or stirling engines), low-maintenance, renewable energy source that are simple to install, safe to store, and cost-effective.
For more than 20 years, the laboratory L3M has acquiered a big experience in thermoelectricity (TE), mainly in thin films and bulk technologies. Moreover, for 10 years, L3M has also acquiered a strong experience in additive manufacturing (AM), mainly for metallic materials. The use of AM for TE offers new perspectives, and enables to create new and original geometries (leading to an optimization of yield and/or a better integration), with less materials losses, a significant decrease of the integration and interface challenges, a faster manufacturing time, a lower cost and the possibility to manufacture TE devices very quickly compared to other technologies. The main barrier consists in obtaining materials with as good quality (in terms of density and microstructure) as with other technologies, which will be possible thanks to a deep development and understanding of the process.
L3M has started this new technology for 3 years. Researches are focused on TE materials based on silicon-germanium alloys, which are very good materials for high temperatures applications (500K to 700K) as for spatial, metalworking industry, etc.
The objective of this PhD study will be, from one side, to continue current studies about optimization of SiGe manufacturing process by AM (and more specifically by Laser Powder Bed Fusion (L-PBF) technology), and from the other side, to manufacture the first TEG demonstrators. For the first part, the study will have to lead to the understanding of the specifities of AM mechanisms on SiGe structural properties. This structural study will include measurement of mechanical properties, as well as microscopic analysis. This study will be also correlated to experimental measurements of manufactured materials TE properties (Seebeck coefficient, electrical and thermal properties).
For the second part, TE generator manufacturing needs to associate two TE materials (n- and p-type SiGe) and assemble together, by optimizing electrical contacts between these two materials. CEA-Liten has deposited a patent about the original manufacturing of such device by AM. The realisation and electrical characterization of a TE generator will be also developed in the framework of this study, leading to highlight advantages of this manufacturing technique.
It should be noted that this work will be performed in the framework of a European project launch.