Influence of the ratio of sintering aids on the properties of porous Si3N4 ceramics fabricated by digital light processing

Abstract

The sintering aids play an important role in affecting the properties of porous Si3N4 ceramics. However, there are few researches on the properties of porous Si3N4 ceramics fabricated by digital light processing (DLP) with different ratios of sintering aids. In this paper, porous Si3N4 ceramics with different ratios of sintering aids (Y2O3-Al2O3) were formed by DLP technology. The influence of Y2O3-Al2O3 ratios on the properties of Si3N4 slurry and porous ceramic was studied systematically. The ratio of Y2O3-Al2O3 had little effect on the rheology and cure depth of Si3N4 slurry due to the low addition of sintering aids. The increase of Y2O3-Al2O3 ratio promoted the anisotropic growth of β-Si3N4. When the ratio of Y2O3-Al2O3 was 9:1, the aspect ratio of β grains reached the maximum. As the ratio of Y2O3-Al2O3 powders increased, the linear shrinkage of porous Si3N4 ceramics showed an increasing and then decreasing trend in three directions. When the Y2O3-Al2O3 ratio was 3:7, the shrinkage rate in the length, width and height direction reached the maximum (27.03%, 30.27% and 40.02%, respectively). The bulk density and flexural strength exhibited an initial increase followed by a subsequent decrease, while the porosity showed the opposite trend. When the Y2O3-Al2O3 ratio was 9:1, the porosity reached a maximum of 28.1%. And the bulk density and flexural strength were 2.42 g/cm3 and 421.58 MPa, respectively. This study is of great significance as it lays the experimental foundation in the performance control of porous Si3N4 ceramics fabricated by DLP.