Fabrication and flexural strength of porous Si3N4ceramics with Li2CO3and Y2O3as sintering additives

By employing sintering additives of Li(2)CO(3)and Y2O3, porous Si3N ceramics are prepared after experiencing the processes of sintering and post-vacuum heat treatment at 1680 and 1550 degrees C, respectively. The experimental results demonstrate the completed phase transformation from alpha to beta-Si(3)N(4)in Si(3)N(4)ceramic samples with a amount of 1.60 wt% Li2CO3(0.65 wt% Li2O) and 0.33 wt% Y(2)O(3)additives. The as-synthesized porous Si3N4 ceramics exhibit high flexural strength ((126.7 +/- 2.7) MPa) and high open porosity of 50.4% at elevated temperature (1200 degrees C). These results are attributed to the significant role of added Li(2)CO(3)as sintering additive, where the volatilization of intergranular glassy phase occurs during sintering process. Therefore, porous Si(3)N(4)ceramics with desired mechanical property prepared by altering the addition of sintering additives demonstrate their great potential as a promising candidate for high temperature applications.