Abstract
Effects of grain boundary phases on densification and thermal conductivity of AlN ceramics sintered with various sintering additives were investigated by means of XRD analysis, SEM observation, shrinkage, density, and thermal conductivity measurements. For samples of AlN with 3wt%Y2O3-1wt%CaO-0.25wt%LaB6 or AlN with 3wt%Y2O3-1wt%CaO-0.25wt%AlB2, complete densification was achieved at 1600oC-4h in N2 atmosphere, while the densification was achieved at 1750oC-1h for samples AlN with 2wt%Y2O3-3wt%Al2O3. However, the densification was never achieved in spite of 1800oC temperature for samples of AlN with 5wt% MgO. Differences were found among the achievements of those densifications. These differences should depend on the temperature of liquid phase′s formation, according to the phase diagram of these additives.
