Effect of the various oxide additives on the microhardness of silicon nitride ceramics

This article describes the effects of aluminum, yttrium and magnesium oxides on the microhardness of silicon nitride ceramics. Such methods as spark plasma sintering and standard sintering in a nitrogen atmosphere for a short time were chosen. The temperature range near the phase transformation of silicon nitride for spark plasma sintering was investigated as the most relevant. It was shown that ceramics produced by spark plasma sintering have a higher microhardness compared to the microhardness of the similar materials obtained by free sintering in the nitrogen. Pressureless sintered ceramics with the magnesium oxide had a higher microhardness compared to the microhardness of the ceramics manufactured by the same method at a lower temperature with yttrium oxide. Materials obtained by spark plasma sintering were distinguished by an extremely high microhardness regardless of the additive type. Spark plasma sintered ceramics with yttrium oxide had a minimum microhardness.