Liquid-Phase Sintering of Alumina Coated with Magnesium Aluminosilicate Glass

Densification of alumina coated with a MgO‐Al 2 O 3 ‐SiO 2 (MAS) glass was investigated from 1400° to 1460°C. Spinel was observed to form at the liquid‐alumina interface, whereas mullite crystallized uniformly in the liquid. Spinel and mullite crystallization kinetics were accelerated by smaller alumina particle size. Mullite and spinel crystallization retarded densification by forming a percolating network. Boron doping suppressed spinel formation, and thus alumina sintered to higher densities at low temperature. The concept of glass basicity is proposed as a useful guide for selecting dopants for low‐temperature sintering.