Si3N4 ceramics sintered with Y2O3/SiO2 and R2O3(ss)/SiO2: a comparative study of the processing and properties

a comparative study was made of si3n4 sintered with two types of additives, namely, y2o3/sio2 and r2o3(ss)/sio2, r2o3(ss) being a rare earth metal oxide in solid solution. the processing conditions for both types of si3n4 were 14 vol% of additives and a sintering temperature of 1800 oc for 30, 60 and 240 min. to compare the efficiency of the additives in the material's sintering process, the density, flexural strength, fracture toughness and hardness were measured and the phase composition and microstructure determined. the results indicated that r2o3(ss)/sio2 as a sintering aid improved the material's high temperature strength and slowed down grain growth when compared with the y2o3/sio2 additive.