The Anisotropic Properties of the Tape Cast Si3N4 Ceramics with Rod-Like β-Si3N4 Seeds Addition
Lu2O3 and SiO2 were used as sintering additives and rod-like β-Si3N4 seeds were added to enhance β-Si3N4 grain unidirectional growth. Silicon nitride ceramics were prepared by tape casting and gas pressure sinteringat 1950oC in 10 atm nitrogen atmosphere for 6 h. Compare to the no-seeded Si3N4, the seeded and tape-cast Si3N4 ceramics have obvious anisotropic microstructure and anisotropic properties. When a stress applied along with the grain alignment direction, the bending strength of the seeded and tape-cast Si3N4 at 1500oC was 738 MPa, which was almost the same as its room temperature bending strength. However, the bending strength of the seeded and tape-cast at room temperature was 556 MPa (perpendicular direction); and their thermal conductivity were 67 W/m·K (perpendicular direction) and 83 W/m·K (parallel direction), respectively. The anisotropic properties of the seeded and tape-cast Si3N4 were attributable to the elongated Si3N4 grain alignment.
T. Ohji, T. Sekino and K. Niihara
Y. P. Zeng et al., "The Anisotropic Properties of the Tape Cast Si3N4 Ceramics with Rod-Like β-Si3N4 Seeds Addition", Key Engineering Materials, Vols. 317-318, pp. 593-596, 2006