Intensive particle rearrangement in the early stage of spark plasma sintering process

The densification behaviors of 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) ceramics during spark plasma sintering (SPS) were analyzed both using the master sintering curve (MSC) approach and by evaluating the temperature dependent evolution of density and densification rate. It was found that densification curves could hardly be fitted using one apparent activation energy value by MSC conception, by which it indicated that more than one densification mechanisms were involved in SPS. Moreover, dependent neither on applied pressure (20–100 MPa) nor heating rates higher than 50 °C/min, the maximum densification rate had always been observed at rather similar ∼78% of theoretical density (TD) accompanied with negligible grain growth. An intensive particle rearrangement mechanism was proposed to dominate the rapid densification to 78% TD in early stage of SPS process, by which it yielded the considerable faster densification rate than those achievable by diffusion-related processes.