Low‐Temperature Preparation of β‐ Si 3 N 4 Porous Ceramics with a Small Amount of Li 2 O – Y 2 O 3

Porous β‐ Si 3 N 4 ceramics are sintered at 1600°C in N 2 and postheat treated at 1500°C under vacuum using Li 2 O and Y 2 O 3 as the sintering additives. The partial sintering and phase transformation are promoted at low temperature by the addition of Li 2 O . The addition of Y 2 O 3 is advantageous for the formation of high aspect ratio β‐ Si 3 N 4 grains. After postheat treatment, a large amount of intergranular glassy phase is removed, and the Li content in the samples is decreased. By this method, the β‐ Si 3 N 4 porous ceramic with a porosity of 54.1% and high flexural strength of 110 ± 8.1 MPa can be prepared with a small amount of sintering additives, 0.66 wt% Li 2 O and 0.33 wt% Y 2 O 3 , and it is suitable for high‐temperature applications.