Properties of SiC Ceramics Sintered via Liquid Phase Using Al₂O₃ + Y₂O₃, Al₂O₃ + Yb₂O₃ and Al₂O₃ + Dy₂O₃ as Additives: a Comparative Study

Silicon carbide (SiC) ceramics show excellent performance at high temperatures. Due to the high covalence of Si-C bonds, these ceramics are produced successfully only via liquid phase sintering (LPS). In this work, SiC ceramics were sintered via LPS using eutectic mixtures of Al₂O₃+Y₂O₃, which served as a standard for comparison, Al₂O₃+Yb₂O₃ and Al₂O₃+Dy₂O₃. The oxides mixtures were used to form liquid phase during the SiC sintering. Mixtures of SiC and additives were ground, pressed at 300 MPa and sintered at 1950ºC for 2 hours. All mixtures showed similar hardness, fracture toughness and flexural strength slightly different. Also the microstructure and crystalline phase were similar, showing that the ytterbium's and dysprosium's oxides can be also used as additive as well the most used oxide, yttrium oxide.

silicon carbide; liquid phase sintering; rare earths oxide; mechanical properties