Microstructure and properties of porous Si₃N₄ ceramics fabricated by digital light processing combined with spark plasma sintering

Sintering process is an important factor affecting the properties of porous Si₃N₄ ceramics. However, there are few studies on the properties of porous Si₃N₄ ceramics fabricated by combining digital light processing (DLP) technology and spark plasma sintering (SPS) technology. In this study, a method to prepare porous Si₃N₄ ceramics by combining DLP with SPS technology was proposed, and ceramic samples were successfully prepared. The effect of sintering temperature and holding time of SPS technology on the microstructure and properties of porous Si₃N₄ ceramics prepared by DLP technology was discussed. With the increase of sintering temperature from 1600 °C to 1700 °C, the conversion content of α-Si₃N₄ phase to β-Si₃N₄ phase increased from 19.19% to 76.72%. The fracture mode of porous Si₃N₄ ceramics gradually transformed from intergranular to transgranular. The porosity of Si₃N₄ ceramics gradually decreased from 40.34 ± 4.9% to 30.54 ± 2.7% with opposite trend in bulk density. And the flexural strength increased from 109.1 ± 7.6 MPa to 249.5 ± 4.0 MPa. When the sintering temperature was 1700 °C, the content of β-Si₃N₄ increased first and then remained essentially constant with the increase of holding time from 5 min to 15 min. The porosity increased from 30.54 ± 2.7% to 35.15 ± 2.5%, while the variation in bulk density were opposite. And the flexural strength severely decreased from 249.5 ± 4.0 MPa to 126.1 ± 7.2 MPa. This research provides valuable insights into the DLP-forming ceramic materials sintered by SPS technology.