Effect of La2O3-MgO ratio on the microstructure and properties of Si3N4 ceramics fabricated via digital light processing

Due to the low powder content characteristic of digital light processing in the preparation of ceramic green bodies, significant challenges arise in obtaining high-density, high-performance Si 3 N 4 ceramic. Sintering aids exert a critical influence on the densification and properties of Si 3 N 4 ceramics. To further improve the performance of 3D-printed Si 3 N 4 ceramics, Si 3 N 4 ceramics were fabricated using DLP technology combined with gas pressure sintering employing different ratios of La 2 O 3 -MgO as sintering aids. The ceramic slurries, microstructures, and ceramic performance were studied systematically. The results showed that increasing the proportion of· La 2 O 3 powder enhanced the rheological and curing properties of Si 3 N 4 ceramic slurries. Varying the La 2 O 3 -MgO ratio affected the composition of the liquid phase, leading to differences in the densification and grain growth of Si 3 N 4 ceramics. The average grain size increased with higher ratios of La 2 O 3 -MgO, and reached a maximum value of 0.91 μm with a ratio of 9:1. With the increase of the La 2 O 3 -MgO ratio, the bulk density and shrinkage rate of the ceramics initially increased and then declined. In addition, the flexural strength and fracture toughness of the ceramics peaked at a ratio of 3:7 for La 2 O 3 -MgO, measuring 577 ± 16.28 MPa and 5.84 ± 0.17 MPa m 1/2 , respectively. These results demonstrate that high-performance Si 3 N 4 ceramics can be effectively prepared using DLP technology by adapting the ratio of sintering additives.