Effect of samarium oxide doping on the chromaticity and mechanical performance of hot-press sintered silicon nitride ceramics

In this study, the effects of Sm 2 O 3 doping on the properties of silicon nitride ceramics were systematically investigated. The results demonstrated that Sm 2 O 3 doping significantly modified the crystal structure, grain boundary characteristics, and color evolution of silicon nitride ceramics, thereby, synergistically enhancing both structural and functional properties. XRD analysis confirmed the complete transformation of α -Si 3 N 4 to β -Si 3 N 4 . Due to the larger lonic radius of Sm 3+ compared ton Si 4+ , lattice expansion occurred, inducing residual stress at grain boundaries or within the grains. This residual stress effectively hindered the propagation of primary cracks, thus improving the facture toughness. Optimal performance was achieved at a doping concentration of 6 wt .%, resulting in the Vickers hardness of 15.91 GPa and the fracture toughness of 15.98 MPa·m 1/2 . Within the visible spectrum, the color of the ceramic sample evolved from light gray to reddish-brown, attributed to the 4 f electronic transitions of Sm 3+ . Moreover, the formation of the stable transfer layer significantly reduced frictional losses, while the material exhibited minimal overall deformation and enhanced frictional stability.