LIQUID-PHASE SINTERING OF ALUMINA-COATED WITH MAGNESIUM ALUMINOSILICATE GLASS

Densification of alumina coated,vith a MgO-Al2O3-SiO2 (MAS) glass was investigated from 1400 degrees to 1460 degrees C. Spinel was observed to form at the liquid-alumina interface, whereas mullite crystallized uniformly in the liquid. Spinel and mullite crystallization kinetics w ere accelerated by smaller alumina particle size. Mullite and spinel c rystallization 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-temperatur e sintering.