Sintering behavior of gehlenite, part II. Microstructure and mechanical properties

A self-toughened gehlenite (2CaO·Al₂O₃· SiO₂ or "C₂AS") ceramic with randomly distributed platelet grains was prepared by the organic steric entrapment (PVA) route. The gehlenite ceramic had a density of 2.698-2.875 g/cm³, corresponding to a relative density of 90%-96%. The platelet gehlenite grains had an average thickness of 3.6±0.8 μm and a width of 12.9±3.7 μm, respectively, with an average aspect ratio of 3.6. The three-point bending strength, fracture toughness, and Young's modulus attained were 142.1±12.1 MPa, 2.32±0.12 MPa·m^1/2, and 108±6.8 GPa, respectively. Fractography as well as Vickers indentation crack propagation profiles showed that crack deflection, crack blunting, and pinning effects due to the randomly distributed platelet grains were considered to be responsible for the good mechanical properties of the gehlenite ceramic.