Spark plasma sintering of translucent polycrystalline α/β-silicon nitride ceramics with Y2O3 additive

Translucent polycrystalline alpha/beta-silicon nitride ceramics had been fabricated for the first time by spark plasma sintering from alpha-Si3N4 starting powder with 2 wt% Y2O3. It aimed to investigate the influence of process pa-rameters on the phase evolution, microstructural development, and mechanical properties of sintered ceramics. The increase in sintering temperature from 1750 degrees C to 1800 degrees C under 25 MPa considerably raised relative density, promoted alpha-beta phase transformation, increased hardness and fracture toughness values, and exhibited translucency in the visible region. Furthermore, the highest relative density (98%), hardness (-HV: 14.9 GPa), fracture toughness (-9.8 MPa m1/2) values, and a higher degree of translucency were achieved with the increment of uniaxial pressure from 25 to 50 MPa at 1750 degrees C. These results indicated that translucent poly-crystalline alpha/beta-silicon nitride ceramics, produced by liquid phase assisted spark plasma sintering at 1750 degrees C under 50 MPa, can be used as transparent armors and visible windows under harsh conditions.

Automated summary

Translucent polycrystalline alpha/beta-silicon nitride ceramics were fabricated for the first time using spark plasma sintering. The process parameters had a significant influence on the phase evolution, microstructure development, and mechanical properties of the sintered ceramics. Increasing the sintering temperature and uniaxial pressure resulted in higher relative density, improved hardness and fracture toughness, and increased translucency.