Mechanical characterization of highly porous β-Si₃N₄ ceramics fabricated via partial sintering & starch addition

In this study, porous β-Si₃N₄ ceramics containing limited amount of Sm₂O₃ and CaO as sintering aids were produced by addition of potato starch (10 and 20vol.%) and partial sintering. Two different Si₃N₄ powders, α- and β-, were used as starting materials. Scanning electron microscopy investigations revealed that development of elongated β-Si₃N₄ grains were much more pronounced when α-Si₃N₄ starting powder was used. Even though porosity values of the compositions prepared by using α-Si₃N₄ (∼57.0-58.4%) is significantly higher than the samples produced by β-Si₃N₄ (42.6%), no significant change was observed for the bending strength, fracture toughness and Weibull modulus. This indicates that microstructural features have a significant contribution to the mechanical properties of the porous materials in terms of bending strength and fracture toughness.