Effects of Y 2 O 3 /MgO ratio on mechanical properties and thermal conductivity of silicon nitride ceramics

In this work, the effects of Y2O3/MgO ratio on the densification behavior, phase transformation, microstructure evolution, mechanical properties, and thermal conductivity of Si3N4 ceramics were investigated. Densified samples with bimodal microstructure could be obtained by adjusting the ratio of Y2O3/MgO. It was found that a low Y2O3/MgO ratio facilitated the densification of Si3N4 ceramics while a high Y2O3/MgO ratio benefited the phase transformation of Si3N4 ceramics. Best mechanical properties (flexural strength of 875 MPa, and fracture toughness of 8.25 MPa·m1/2, respectively) and optimal thermal conductivity of 98.04W/(m·K) were achieved in the sample fabricated with Y2O3/MgO ratio of 3:4 by sintering at 1900°C for 4 h.