Spark plasma sintering of alumina: Study of parameters, formal sintering analysis and hypotheses on the mechanism(s) involved in densification and grain growth

The spark plasma sintering (SPS) of an undoped commercial α-Al2O3 powder (0.14 μm) was investigated. The SPS parameters such as the dwell temperature, applied external pressure, temperature of pressure application, dwell time and pulse pattern were varied. A sintering path (relative density vs. grain size) showing two regimes has been brought to the fore: densification without grain growth occurring at the lower temperatures and grain growth without much further densification taking place at the higher temperatures, with a threshold between 1100 and 1200 °C. In addition, a formal sintering analysis was performed in order to identify the mechanism(s) involved in densification and grain growth.