We are living in a situation that requires a drastic transition to a more sustainable energy system (SDG 2030). The scientific community is making a great effort to improve the efficiency of any type of energy generation process. Nowadays, there is a great interest in obtaining more efficient thermoelectric materials for direct conversion of thermal energy into electricity. From this point of view, firstly, not desirable thermal fluxes can be avoided, which often lead to considerable energy losses and poor efficiency. Secondly, it eliminates the dependence on fossil fuels that are usually necessary to obtain electricity through a thermal process. Finally, thermoelectric conversion does not produce greenhouse gases, which are contributing to the global warming.
So far, bismuth telluride and its alloys with antimony telluride or bismuth selenide have been the most efficient thermoelectric materials used at near room temperature. Some commercial thermoelectric devices and modules, based on bismuth telluride and its alloys have been successfully developed for power generation and solid-state cooling at this temperature range. They are obtained by the zone melting (ZM) method, a time and energy-intensive fabrication process that can lead to changes in composition, thus deteriorating thermoelectric performance. In addition, their low mechanical properties limit their long-term use. Therefore, it is of great interest to develop new fabrication methods of polycrystalline thermoelectric materials with high performance and excellent mechanical reliability based on bismuth telluride with low cost, high efficiency and simple processing.
In this regard, the non-conventional processing of materials by microwave radiation (MW) is presented as a fast, low energy consumption and environmentally sustainable alternative to achieve substantial improvements in the final properties of materials thus, providing  high added value.
The aim of this research is the study and optimization of MW sintering of Bi2Te3 parts using a single-mode device as a more efficient and environmentally friendly process. By controlling the power absorbed by the sample throughout the sintering process, as well as its surface temperature, densification without grain coarsening is achieved.
Dense ceramics have been sintered with a dwell time of 5 min at 340 ºC. The mechanical and microstructural properties were analyzed and compared with their counterparts obtained by Spark Plasma Sintering (SPS). These preliminary results demonstrate the feasibility of non-conventional techniques (MW and SPS) for the rapid consolidation at low temperature of thermoelectric materials.
 
Acknowledgments
This research was funded by projects of Generalitat Valenciana: CIGE/2021/076, BEST/2021/084 and BEST/2021/082.