Porous Si3N4 Fabricated by Phase Separation Method Using Benzoic Acid as Pore-Forming Agent

Porous Si3N4 ceramics with interconnected pores were fabricated by the phase separation method using benzoic acid (BA) as a pore-forming agent. The green bodies were prepared at room temperature under vacuum and pore-forming agent was quickly removed by sublimation below 200°C. The resulting porous green body exhibits uniform distribution of rod-like pores in the matrix. The porosity can be controlled by adjusting the BA content in Si3N4 slurry. The flexural strength and fracture toughness of the porous Si3N4 samples are in the range of 85–126 MPa and 1.08–1.7 MPa·m1/2 with the porosity range of 57%–65.8%.