Sintering Behavior of Hot-Pressed Ca–αSialon Ceramics

Abstract

On the basis of phase relationships in the Ca–Si–Al–O–N system, a Ca–α–sialon ceramic was synthesized using the hot-pressing technique. The reaction sequences and densifications of the Ca–α–sialon vs. firing temperatures have been characterized in detail. The present experiments reveal a reaction sequence as follows: at 1250°C the reactant mixture started to soften, at 1300°C a gehlenite phase was produced, at 1500°C the gehlenite phase was resolved into a liquid phase and a Ca–α–sialon started to form, and at 1600°C the formation of Ca–α–sialon was complete. The product was stable and almost entirely single phase Ca–α–sialon. Accompanying to the above sequences, densification also proceeded via a liquid-phase sintering, particle rearrangement, solution–reprecipitation, and grain growth process. In the final microstructure elongated grains of Ca–α–sialon were obtained, improving the fracture toughness of this Ca–α–sialon ceramic.