Effects Of MgAl_2O_4-ZrO_2 Addition On Sintering Behaviors and Mechanical Properties of Silicon Nitride Ceramics

摘要

The influences of the sintering additive content of MgAl_2O_4-ZrO_2 (total 5-15 mass percent with a MgAl_2O_4/ZrO_2 ratio 1: 1) on sintering behaviors, microstructure and mechanical properties of Si_3N_4 ceramics were investigated. Sintering was carried out in the temperature range of 1200 to 1900 deg 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 percent), both high flexural strength and high fracture toughness could be obtained.