Characteristics of Liquid Penetration into Undoped and Magnesia-Doped Alumina

Liquid-forming impurities (CaO + SiO2) were placed on the top of undoped and MgO-doped Al2O3 powder compacts, and the microstructural evolution and the extent of liquid penetration during heat treatment were investigated. Compared with the undoped specimen, abnormal grain growth was limited and the impurities penetrated more deeply in the MgO-doped specimen. The homogenization of the microstructure and the enhanced liquid penetration in MgO-doped specimens could be explained in terms of an interface roughening or a modification of the liquid-(glass-) phase characteristics, such as viscosity.