Ultrafast high-temperature sintering and thermoelectric properties of n-doped Mg₂Si

Abstract

Ultrafast High-temperature Sintering (UHS) is a recently proposed technique able to synthesize and sinter dense materials within seconds. Although UHS has already proved its effectivity with a large set of materials, spanning from refractory ceramics to complex metal alloys, any application to thermoelectric materials is today still lacking. Mg2Si is a well-established thermoelectric material. It is based on wide available non-critical raw materials, it is non-toxic, lightweight and it express its best thermoelectric performances in the intermediate temperature range (up to about 600 °C). Mg2Si is typically produced with powder processing by Spark Plasma Sintering, partially limiting its widespread diffusion also due to the costly production technique. Here we present a simple route to sinter Mg2Si pressed powders by UHS. The process allowed to obtain dense samples (with relative densities >95%) with 20 seconds heating up to about 1080 °C followed by a rapid free cooling, with a total thermal history below 1 minute, with energy demands at the Wh scale. The high process rate proved its efficacy in preventing grain growth and in avoiding any significant Mg evaporation. A full thermoelectric functional characterization is presented for Mg2Si and Bi-doped Mg2Si, together with a comparison with SPS-produced properties.

Innovations in Electric Current-Assisted Sintering for SOFC: A Review of Advances in Flash Sintering and Ultrafast High-Temperature Sintering

“…UHS, despite its relatively nascent development, is already finding applications across various fields. It is currently utilized in the production of SOFC, solid electrolytes [145,146], polymer-derived ceramic nanocomposites (PDC-NC) [147], thermal barrier coating materials [41,148,149], thermoelectric nanomaterials [150], metal and alloy materials [151], biomaterials [152], and quartz glass [153], etc. FS, with its broad applicability, extends beyond SOFCs and solid electrolytes [154] to include semiconductor materials [55], metalliclike conductors such as borides, nitrides, and carbides of transition metals [113], armor [155,156], biomaterials [157,158], the joining of dissimilar materials [159,160], and nuclear fuel [161][162][163].…”

Editorial: focus on waste-heat harvesting via thermoelectric conversion: materials, devices and systems for sustainable energy technologies

“…Sustainable materials containing earth-abundant and low-cost elements are the most represented in the collection: among them, binary [1] and multinary [2] chalcogenides, skutterudites [3,4], half-Heusler phases [2,5] and silicides [6].…”

“…The advantage of the ultrafast high-temperature technique is also the low energy involved, resulting in a low production cost. In the case of silicides, such as Mg 2 Si, a non-toxic and low-cost material, the UHS technique proved to process dense samples while limiting grain growth and Mg evaporation, with low energy demand [6].…”