Flash microwave sintering of alumina

International audienceConventional flash sintering is difficult to adapt to ceramics with a very low electrical conductivity like pure alumina. Alternatively, the latter can be heated by microwave/matter interaction due to dielectric losses. Microwave energy is also preferable as it allows a rapid contactless and volumetric heating that can be initiated by susceptors. This work presents the assembly designed for this purpose by using a 2.45 GHz single-mode microwave cavity and the original assembly of susceptors made from silicon carbide plates and a 3D printed zirconia crucible. Controlled thermal cycles ranging from 300 to 900 K/min were successfully applied while measuring the shrinkage during the flash sintering. Alumina pieces were successfully sintered up to 93-98 % in mere seconds, depending on the heating rates, and microstructures were discussed according to the microwave "flash" heating conditions originally applied