Oxidation behaviour of a hot isostatically pressed silicon nitridematerial

The oxidation behaviour of a dense silicon nitride material containing the minimum amount of additives was studied. A silicon nitride powder was hot isostatically pressed in the presence of 0.5 wt% Y2O3 and 0.025 wt%Al2O3. The dense material obtained was oxidized for 24 hours, in an oxygen atmosphere within the temperature range 1475-1650°C. The high oxidation resistance of this material may be related to the low amount of sintering aid initially introduced and consequently to the composition of the grain boundary phase. According to the temperature, the apparent activation energies for the oxidation processes, ranged from 355 to 680 kJ/mole