Mechanical and thermal properties of silicon carbide ceramics with yttria-scandia-magnesia

Two different SiC ceramics with a new additive composition (1.87 wt% Y2O3-Sc2O3-MgO) were developed as matrix materials for fully ceramic microencapsulated fuels. The mechanical and thermal properties of the newly developed SiC ceramics with the new additive system were investigated. Powder mixtures prepared from the additives were sintered at 1850 degrees C under an applied pressure of 30 MPa for 2 h in an argon or nitrogen atmosphere. We observed that both samples could be sintered to >= 99.9% of the theoretical density. The SiC ceramic sintered in argon exhibited higher toughness and thermal conductivity and lower flexural strength than the sample sintered in nitrogen. The flexural strength, fracture toughness, Vickers hardness, and thermal conductivity values of the SiC ceramics sintered in nitrogen were 1077 +/- 46 MPa, 4.3 +/- 0.3 MPa.m(1/2), 25.4 +/- 1.2 GPa, and 99 Wm(-1) K-1 at room temperature, respectively.