Effects of Y2O3 and Al2O3 Addition on the Properties of Hot Pressed AIN Ceramics

AN plates were fabricated by hot pressing at 1700-1900 degrees C using yttria and alumina (3 and 10 mu m particle size) powders as additives and characterized: density, thermal conductivity, transverse rupture strength, and grain size measurement by SEM and EDS. Density values of 3.31-3.34 g/cm(3) are largely attributed to hot pressing of powder mixtures in carbon mold under N2 atmosphere which caused effective degree of oxygen removal from yttrium-aluminate phase expected to form at 1100 degrees C. The grain size of hot pressed AIN was almost homogeneous, with size approximately from 3.2 to 4.0 mu m after hot pressing. Al2O3 powder of 3 mu m particle size resulted in better transverse rupture strength and finer grain SIze compared to 10 pin Al2O3 powder. The thermal conductivity of AIN ranged between 83-92.7 W/m center dot K and decreased with Al2O3 addition. Fine grain size is preferred for better mechanical properties and thermal conductivity.