A novel method to fabricate porous single phase O’-sialon ceramic and improve its mechanical property

Nowadays, the O?-sialon ceramics are synthesized by the reaction of Si3N4, SiO2 and Al2O3. However, it is difficult to achieve the single phase materials. Here, we have successfully developed porous single phase O?-sialon ceramics by pre-oxidation combined with gas-pressure sintering method. The effects of ?-Si3N4 powder on the microstructure, phase evolution, mechanical property were investigated. The result illustrated that the main crystal phase of the porous ceramics was composed of the single O?-sialon phase. The pores were well distributed and generated from the decomposition of Si2N2O. The elongated O?-sialon grains were found and formed around pore walls. Additionally, the addition of ?-Si3N4 powder was beneficial for improving the bending strength because of the reduction of porosity and pore size. The porous O?-sialon ceramics with uniform pores obtained the excellent bending strength when the ?-Si3N4 powder was 6 wt%.