Anisotropy of Grain Growth in Alumina

Grain growth in theoretically dense undoped and MgO-doped polycrystalline Al2O3 was studied, and average grain-boundary migration rates were compared with those of a-plane and c-plane sapphire during migration into the same undoped and MgO-doped materials. The results are discussed in terms of a grain-size-dependent grain-boundary mobility-grain-boundary energy product, Mbγb. The grainsize dependencies of the Mbγb products for seed and matrix grains differ. Seed orientation appears to affect the nature of solute-boundary interactions. The importance of grain-boundary structure on migration characteristics is also indicated by a demonstration of twin-formation-enhanced grain growth