Mechanical Properties of Ce₀.₉Gd₀.₁O₂₋ₓ and Ce₀.₉Gd₀.₁O₂₋ₓ+Al₂O₃ Composites

The room-temperature elastic moduli, fracture strength, and fracture toughness of dense, fine-grained, pure Ce _0.9 Gd _0.1 O _1.95 and composites containing 1.3 and 9.1 wt.% Al ₂ O ₃ were investigated. Addition of 9.1 wt.% Al ₂ O ₃ to Ce _0.9 Gd _0.1 O _1.95 changed the fracture mode from intergranular to transgranular and increased room-temperature fracture strength from 65 to 125 MPa and fracture toughness from 1.3 to 1.6 MPam ^1/2 . In addition, steady-state compressive creep was measured for Ce _0.9 Gd _0.1 O _1.95 and the Ce _0.9 Gd _0.1 O _2-x +9.1 wt.% Al ₂ O ₃ composite. The stress exponent ≈1.3 and the activation energy ≈480 kJ/mole for Ce _0.9 Gd _0.1 O _1.95 suggested diffusional flow controlled by the cations. There was no difference in creep rate between Ce _0.9 Gd _0.1 O _2-x and the composite.