LAUSR

Pressureless sintering of Si3N4 doped with 2 mol% Y2O3 and 5 mol% MgO was carried out at temperatures ranging from 1700°C to 1770°C in three kinds of packing powders consisting of Si3N4 and BN coupled with or without addition of Y2O3, MgO, and SiO2. Effects of packing powders on weight change, densification, and grain growth during sintering and properties (thermal conductivity, fracture toughness, and bending strength) of the sintered samples were studied. It was found that adding Y2O3 and MgO into the packing powder resulted in improvement of densification, grain growth, thermal conductivity, fracture toughness, and bending strength of the sintered samples. However, further addition of SiO2 into the packing powder could lead to suppressed grain growth and decrease in thermal conductivity, fracture toughness, and bending strength. The sample sintered at 1770°C in the packing powder containing Y2O3 and MgO was fully densified, and it possessed well‐balanced properties: thermal conductivity of 76 W m−1 K−1, fracture toughness of 7.82 MPa m1/2, and bending strength of 932 MPa.