Advanced Powder Metallurgy for the Manufacturing of Fe2VAl-Based Thermoelectric Generators

The electrification of our society relies on the availability of distributed sources of clean energy to power numerous systems, devices, and sensors. Surrounding thermal energy offers such an opportunity through the use of thermoelectric generators, as thermoelectric materials can convert heat directly into electricity. However, commercially available solutions are generally based on rare, expensive, or even toxic elements, which limits their potential for large-scale applications. In contrast, Fe2VAl-based compounds rely on inexpensive and widely available elements. Although extensive research has been devoted to understanding and optimizing their thermoelectric properties, significant challenges remain from a processing perspective, particularly for the scalable fabrication of Fe2VAl-based generators. This thesis aims to investigate powder metallurgy-based routes to simplify the manufacturing of Fe2VAl-based thermoelectric generators. Fe2VAl was processed using an additive manufacturing technique known as Laser Powder Bed Fusion, which enables the fabrication of net-shape parts with promising throughput. Although as-printed samples exhibit numerous transverse cracks, solutions such as the use of a preheated printing substrate or post-processing heat treatments were shown to be effective in either preventing crack formation or healing existing cracks. The sintering of Fe2VAl and its co-sintering with various metals were also studied. Co-sintering was shown to enable the fabrication of Fe2VAl–metal junctions with low electrical contact resistivity that remain stable under nominal operating conditions of a thermoelectric generator. Finally, co-sintering was found to be suitable for the fabrication of transverse thermoelectric generators, which are assumed to exhibit simplified geometries. This type of generator was extensively investigated through modeling, and several prototypes were fabricated by co-sintering and experimentally characterized using an in-house developed measurement system.