Densification kinetics of flash sintered 3mol% Y₂O₃ stabilized zirconia

Flash sintering is an attractive technique that is capable of rapidly sintering ceramics, although its densification mechanism is arguable. Hence, studies involving the kinetics of flash sintering are crucial in providing insights into the ultrafast densification process. In this work, a 3mol% Y₂O₃ stabilized zirconia (3YSZ) was used as a model compound for determining flash sintering densification kinetics. Shrinkage of 3YSZ samples during the flash sintering process at 900 °C was recorded as a function of applied current density. Activation energy for the flash densification process was determined based on the conventional densification theory. Results indicated that the injected oxygen vacancies at the incubation stage had a direct influence on the densification activation energy. In contrast, the densification during the flash sintering stage appeared to be dominated by the migration of oxygen vacancies under an electric field. This was inferred upon by the comparison of activation energies for the densification and conduction processes. Based on this finding, we propose that flash densification results from the movement of oxygen vacancies to form different charged defects that have an electrostatic interaction between them.