Densification mechanism of stereolithographical dense Si3N4 ceramics with CeO2 as sintering additive by field assisted sintering

Combining sintering additive with field assisted sintering, stereolithographical dense Si 3 N 4 ceramics was successfully fabricated. Owing to a large amount of polymer during the stereolithography, the green parts have the characteristics of low powder loading and high porosity. Adjusting the process parameters such as sintering temperature and soaking time can effectively improve the density of the specimens. The stress exponent n of all specimens is in a range of 1 and 2, which is derived from a modified sintering kinetics model. The apparent activation energy Q d of stereolithographic Si 3 N 4 ceramics sintered with applied pressures of 30 MPa, 40 MPa, and 50 MPa is 384.75, 276.61 and 193.95 kJ/mol, respectively, suggesting that the densification dynamic process is strengthened by raising applied pressure. The grain boundary slipping plays a dominating role in the densification of stereolithographic Si 3 N 4 ceramics. The Vickers hardness and fracture toughness of stereolithographic Si 3 N 4 ceramics are HV10/10 (1347.9±2.4) and (6.57±0.07) MPa·m 1/2 , respectively.