Microstructural Evolution and Mechanical Properties in Yb 2 O 3 –Fluxed Silicon Nitride Ceramics

Silicon nitride ceramics were fabricated with Yb2O3 as the sintering additive. The effects of the amount of Yb2O3 on the microstructure and the mechanical properties such as the flexural strength and the fracture toughness were investigated. Almost fully densified Si3N4 was obtained when only 4 wt% Yb2O3 was added. Both the flexural strength and the fracture toughness increased steadily with the Yb2O3 content. The transgranular fracture mode was observed in the specimen containing 4 wt% Yb2O3, however, the intergranular fracture mode was observed in the specimen containing 10 wt% Yb2O3.