Effects of MgAl2O4-ZrO2 addition on sintering behaviors and mechanical properties of silicon nitride ceramics

Abstract

The influences of the sintering additive content of MgAl2O4-ZrO2 (total 5-15 mass% with a MgAl2O4/ZrO2 ratio 1:1) on sintering behaviors, microstructure and mechanical properties of Si3N4 ceramics were investigated. Sintering was carried out in the temperature range of 1200 to 1900°C. Densification was enhanced with increasing sintering additive content due to an improved particle rearrangement; however, phase transformation and grain growth were significantly suppressed. The phase transformation and grain growth occurred through a solution-reprecipitation mechanism controlled by a diffusion process in this additive system. With the addition of a small amount of the above-mentioned additive mixture (5 mass%), both high flexural strength and high fracture toughness could be obtained.