Strength and Creep Behavior of Rare-Earth Disilicate-Silicon Nitride Ceramics

The flexural strength and creep behavior of RE2Si2O7–Si3N4 materials were examined. The retention in room‐temperature strengths displayed by these ceramics at 1300°C was 80–91%, with no evidence of inelastic deformation preceding failure. The steady‐state creep rates, at 1400°C in flexural mode, displayed by the most refractory materials are among the lowest reported for sintered Si3N4. The creep behavior was found to be strongly dependent on residual amorphous phase viscosity as well as on the oxidation behavior of these materials. All of the rare‐earth oxide sintered materials, with the exception of Sm2Si2O7–Si3N4, had lower creep strains than the Y2Si2O7–Si3N4 material.