Effects of Sm₂O₃ Content on the Microstructure and Mechanical Properties of Post-Sintered Reaction-Bonded β-SiAlON

β-SiAlON materials were fabricated by a reaction bonding combining post-sintering route using raw materials of Si, Al₂O₃, AlN, etc. Sm₂O₃ was used as sintering additive with the content of 0, 2, 4, and 6 wt.%, respectively. The reaction-bonded β-SiAlON (RB-β-SiAlON) were post sintered at 1750 °C for 6 h. XRD results showed that the phase composition of both RB-β-SiAlON and post-sintered RB-β-SiAlON (PSRB-β-SiAlON) was β-SiAlON. For RB-β-SiAlON, the apparent porosity was decreased with the increase of Sm₂O₃ content, while the bending strength (σ_f) and Vicker’s hardness (HV10) was increased accordingly. After the post-sintering procedure, nearly full densified PSRB-β-SiAlON was obtained and the mechanical properties were significantly improved with the addition of Sm₂O₃ additive. The σ_f and HV10 of the PSRB-β-SiAlON (4 wt.% Sm₂O₃) achieved 520 MPa and 16.4 GPa, respectively, which were as 3.5 and 6.3 times high as those of the corresponding RB-β-SiAlON. The Young’s modulus (E) and the fracture toughness (K_IC) of the dense PSRB-β-SiAlON were increased with the increase of the Sm₂O₃ content.