Introduction of nanosized oxides in Mg2Si thermoelectric materials by Spark Plasma Sintering

The magnesium silicides (Mg2Si) based alloys are promising candidates for thermoelectric (TE) energy conversion at temperatures ranging from 500 K to 800 K. Compared with other materials working in the same temperature range, such as lead-based TE materials, Mg2Si is characterized by non-toxicity, low cost, and low density. Another advantage of these materials is abundance of their constituent elements in the earth's crust. Recently, the oxide incorporation effect in this kind of materials was studied, but literature counts only few papers [1, 2] about this controversial topic, probably due to the difficulty to preserve the oxide structure during the sintering processes. This work reports the oxide incorporation in Mg2Si-based materials starting from commercial Mg2Si and commercial metal oxides by means of ball milling and Spark Plasma Sintering (SPS) process. The SPS conditions, in particular the sintering temperature, the pressure and the holding time, were optimized with the aim to obtain both the material full densification and the oxide incorporation, preventing the reduction process previously reported in literature [1]. The morphology, composition and crystal structure of the samples were characterized by FE-SEM, EDS and XRD analyses.