Optimizing sustainable thermoelectric materials for 300-600 K applications

Kurzfassung

One of the world’s greatest global issues is the energetic crisis. As we evolve and grow as a society, new technologies become available and more affordable, consequently the energetic demand increases. In this sense, thermoelectric materials (TE), which can convert heat into electricity and vice-versa through the thermoelectric phenomena, emerge as an elegant solution to mitigate this global issue, as they can be employed for power production from (waste) heat. Moreover, TE devices are maintenance-, noise- and vibration-free, easily scaled-up or down, and can be implemented to a wide range of working temperatures, thus allowing them to be used in various fields ranging from biosensors to space applications [1]. Nevertheless, most commercially available TE devices are composed of costly and/or toxic elements (e.g. Bi2Te3, PbTe) [2]. Hence, it is imperative to find more sustainable solutions, with a competitive thermoelectric performance. Magnesium-based materials, such as Mg2X (X=Si,Sn), seem to fit the requirements, they are made from earth-abundant, cheap and environmental friendly elements, with a good thermoelectric performance at high temperature (600-800 K) [3]. The aim of this work is to optimize Mg2X (Mg2Si1-ySny, y=0.3-1.0) for usage between room temperature and 600 K, i.e. shifting the optimum working range to lower temperatures and hence creating a suitable TE material to replace Bi2Te3. For this purpose, a prediction model was employed based on the Boltzmann transport equation, which allows the prediction of optimum thermoelectric properties based on the charge carriers concentration, and exploration of the formation of a solid-state compound throughout the whole composition [1]. Additionally, different synthesis and sintering routes were tested to evaluate their effect on the thermoelectric properties. Thus, by changing the carrier concentration, the model is able to give the corresponding optimized thermoelectric properties for a certain temperature range and according to the predictions of the model, one can adjust the composition to shift the band gap (decrease it), towards Mg2Sn, favoring improved thermoelectric properties at lower temperatures. Results based on the prediction of the model and experimental data will be shown in the poster.