Rapid Densification and Deformation of Li-Doped Sialon Ceramics

Two lithium-doped sialon ceramics were densified and superplastically deformed by spark plasma sintering (SPS). Rapid densification with linear shrinkage rates of approximately 5 × 10^?3 s^?1 were observed for samples heated at a rate of 100°C/min up to ～1400°C under a uniaxial pressure of 40 MPa. Isothermal deformation by SPS-preprepared, fully densified ceramics performed at T ≥ 1450°C yielded strain rates in the order of 10^?2 s^?2. It is suggested that a high heating rate promotes material transport via formation of a nonequilibrated oxygen-rich liquid of low viscosity. This finding most likely holds true for other liquid-phase sintered ceramics as well and has implications for cost-effective manufacturing of ceramic components.