Compressive creep behavior of fine-grained (5 μm) La0.9Sr0.1MnO3with a relative theoretical density between 85 and 90% was investigated over the temperature range 1150–1300 °C in air. The fine grain size, brief creep transients, stress exponent close to unity, and absence of deformation-induced dislocations, suggested that the deformation was controlled by a diffusional creep mechanism. The activation energy for creep of La0.9Sr0.1MnO3was 490 kJ/mole. A comparison of the activation energy for creep of La0.9Sr0.1MnO3with existing diffusion and creep data for perovskite oxides suggested that the diffusional creep of La0.9Sr0.1MnO3was controlled by lattice diffusion of the cations, either lanthanum or manganese.

An experimental self-reinforced hot-pressed silicon nitride was used to examine the effects of microstructure on hightemperature deformation mechanisms during compression testing. At 1575-1625°C, the as-received material exhibited a stress exponent of 1 and appeared to deform by steady-state grain-boundary sliding accommodated by solutionreprecipitation of silicon nitride through the grain-boundary phase. The activation energy was 610 ؎ 110 kJ/mol. At 1450 -1525°C for the as-received material, and at 1525-1600°C for the larger-grained heat-treated samples, the stress exponent was >1. Damage, primarily in the form of pockets of intergranular material at two-grain junctions, was observed in these samples.

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