Strength and Creep Behavior of Rare‐Earth Disilicate–Silicon Nitride Ceramics

Abstract

The flexural strength and creep behavior of RE 2 Si 2 O 7 –Si 3 N 4 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 Si 3 N 4 . 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 Sm 2 Si 2 O 7 –Si 3 N 4 , had lower creep strains than the Y 2 Si 2 O 7 –Si 3 N 4 material.