A new way of fabricating Si3N4 ceramics by aqueous tape casting and gas pressure sintering

Silicon nitride (Si3N4) ceramic was fabricated by aqueous tape casting and gas pressure sintering at 1850 °C for 60 min under a nitrogen atmosphere of 1.5 MPa. Effects of slurry properties on powder compaction and densification of the green tapes were investigated. The slurry of the Si3N4 powder with polyacrylic acid as dispersant showed shear-thinning rheological behavior. Casting of the slurry on glass plate produced flexible green tape with uniform powder distribution after dried in open air. The green tapes had relative high density, small pore size and homogeneous pore size distribution. Due to high compaction of the ceramic particles and homogeneous distribution of the pores in the green tapes, the sintered silicon nitride ceramics reached a relative density up to ∼99%. Elongated growth of β-Si3N4 grains with a small bimodal distribution, gave good flexural strength, elastic modulus and fracture toughness up to 764 MPa, 285 GPa and 7.05 MPa m1/2, respectively, to the silicon nitride (Si3N4) ceramic.