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

Abstract

Translucent polycrystalline α/β‐silicon nitride ceramics had been fabricated for the first time by spark plasma sintering from α-Si3N4 starting powder with 2 wt% Y2O3. It aimed to investigate the influence of process parameters on the phase evolution, microstructural development, and mechanical properties of sintered ceramics. The increase in sintering temperature from 1750 °C to 1800 °C under 25 MPa considerably raised relative density, promoted α-β 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 °C. These results indicated that translucent polycrystalline α/β‐silicon nitride ceramics, produced by liquid phase assisted spark plasma sintering at 1750 °C under 50 MPa, can be used as transparent armors and visible windows under harsh conditions.