Mechanical properties and thermal conductivity of dense β-SiAlON ceramics fabricated by two-stage spark plasma sintering with Al2O3-AlN-Y2O3 additives

Fully dense β-SiAlON ceramics with excellent mechanical properties and good thermal conductivity were fabricated by two-stage spark plasma sintering (SPS) processes without and with applying pressure respectively, using α-Si₃N₄ powder and 6 Al₂O₃-3 AlN-6 Y₂O₃ (in wt.%, label with 636), 424 and 422 additives. In the first stage SPS process without pressure, the relative dense β-SiAlON ceramics with interlock microstructures of elongated grains and density of 3.14?3.18 g cm^?3, hardness of 14.00?14.82 GPa and fracture toughness of 6.00?6.63 MPa m^1/2 were obtained by sintering at about 1600 °C for 20 min. In the second stage SPS process at about 1425 °C for 5 min under pressure of 24 MPa, the fully dese β-SiAlON ceramics with density of 3.22?3.24 g cm^?3, high hardness of 15.68?15.95 GPa, high fracture toughness of 6.38?7.03 MPa m^1/2 and thermal conductivity of 13.5?19.6 Wm^-1K^-1 were obtained. The reaction between the samples and the graphite mold can be avoided in this fabrication method.