Fabrication and Property of Porous Silicon Nitride Ceramics with Y2O3-Yb2O3 Additions

Wave-transparent porous Si3N4 ceramics were fabricated using 9wt% multiple sintering additives of Y2O3 and Yb2O3. The influence of sintering additive composition on the porosity, mechanical properties and microstructure of porous Si3N4 ceramics was investigated. The results showed that the porous Si3N4 ceramics with porosity ranging from 32% to 43% were prepared. For the porous Si3N4 ceramics sintered at 1690°C, flexural strength, fracture toughness and the β-Si3N4 phase content increased as the Yb2O3 content of multiple sintering additives increased from 0 to 9 wt%. In most specimens, microstructures with interlocked fibrous β-Si3N4 grains and uniformly distributed fine pores were obtained with employing scanning electron microscopic examination and X ray diffraction analysis. Sinterability and phase transformation of Si3N4 with more Yb2O3 content were more pronounced than others.