Role of oxygen on the interfacial adsorption sites of Lu and La in β-Si3N4

Abstract Molecular dynamics computer simulations show the important role of oxygen replacing nitrogen at surface sites in the prismatic surface of β-Si3N4 on the adsorption of rare-earth ions from the intergranular film. Such adsorption affects the grain morphology, which plays an important role in mechanical properties. The simulations successfully obtain the correct Lu sites Lu1 and Lu2 on the prismatic surface with O replacement at specific combinations of N surface sites. The results match the experimental high angle annular dark field scanning transmission electron microscopy data. Unlike the Lu results, surface oxidation does not have a large effect on La adsorption sites on the prismatic surface, but does have an influence on the La surface occupancy. The simulation results provide the mechanisms for both the experimental variances observed for the adsorption sites of these two rare-earth additives in the intergranular films and can be used to explain the different grain growth behavior seen experimentally.