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

In this study, porous beta-Si3N4 ceramics containing limited amount of Sm2O3 and CaO as sintering aids were produced by addition of potato starch (10 and 20 vol.%) and partial sintering. Two different Si3N4 powders, alpha- and beta-, were used as starting materials. Scanning electron microscopy investigations revealed that development of elongated beta-Si3N4 grains were much more pronounced when alpha-Si3N4 starting powder was used. Even though porosity values of the compositions prepared by using alpha-Si3N4 (similar to 57.0-58.4%) is significantly higher than the samples produced by beta-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