Pressure-less spark plasma sintering of alumina

The spark plasma sintering (SPS), also known as plasma activated sintering, is a method applicable for rapid sintering of metals and ceramics. The technique is thought of a type of rapid hot pressing, implying that the application of a uniaxial pressure is essential for enhanced densification kinetics. In this study, the efficiency of heat transfer in the SPS process was examined in the absence of mechanical pressure. Conditions for dynamic isotropic heating were established, and the densification and microstructure development sequences of alumina ceramics during pressure-less SPS process were investigated. The influence of early neck formation on the grain morphology and fine structure is also discussed. The study reveals that high heating rate plays an important role in enhancing densification kinetics. The observed principle bears a general implication for increasing the efficiency of conventional pressure-less sintering procedures that are nowadays widely applied in industry.