Abnormal grain growth of alumina

摘要

Abnormal grain growth (AGG) is not one of the intrinsic properties of alumina but rather is an extrinsic property that is controlled by certain impurities that are introduced during powder synthesis, processing, or sintering. When small amounts of glass-forming impurities are introduced, some portion beyond their solubility limits will accumulate at grain boundaries at the final stage of densification, form thin intergranular glass films of thermodynamically stable thickness, and induce the sudden appearance of abnormal grains by increasing the rate of grain-boundary migration abruptly.