Abstract:
It is common for industrial polycrystalline alumina to contain a significant amount of liquid, but it is unclear what dictates the densification temperature. It is proposed that the viscosity of the grain boundary liquid dictates the densification temperature of polycrystalline alumina. To test this hypothesis, two glass chemistries were engineered, one in the invert glass region and one in the normal glass region. In addition, two levels of each chemistry were evaluated to demonstrate that densification is independent of the amount of liquid in the grain boundary. In support of the hypothesis, samples containing a low viscosity liquid densified at 1600 degrees Celsius, whereas samples containing a high viscosity liquid densified at 1700 degrees Celsius. These results illustrate an opportunity to tailor the grain boundary chemistry in order to control the densification temperature for industrial sintering systems.
