A translucent and hard α/β Si3N4 composite hot-pressed at low temperature with an MgSiN2 additive

A translucent α/β Si3N4 composite, consisting of 85% α-Si3N4 and 15% β-Si3N4, was fabricated by hot-pressing at 1563 °C for 1 h, using an MgSiN2 additive. The α/β Si3N4 composite achieves a maximum transmittance of 66% for a 0.42 mm thick specimen in the medium infrared region, which is attributed to its high density and to a small amount of intergranular phase and β-Si3N4. In addition to optical transmittance, the sample showed a very high hardness of 24.0 ± 0.5 GPa.