Spark plasma sintering behavior of AlON ceramics doped with different concentrations of Y2O3

Aluminum oxynitride (AlON) ceramics were fabricated by spark plasma sintering (SPS) from Al2O3, AlN and different concentrations of Y2O3. Fully dense and single-phase AlON ceramics were obtained in a sample doped with 0.6 wt% Y2O3 sintered at 1600 °C. A proper amount of Y2O3 additive can reduce sintering activation energy and enhance sintering activity due to plasma activated effects. Excess Y2O3 would result in the formation of Y3Al5O12 (YAG) as a second phase which decreased grain boundary mobility and prevented grain growth. Vickers hardness slightly increased from 15.9 to 18.1 GPa, whereas fracture toughness firstly increased and then decreased with increased Y2O3 concentration. This work demonstrates that the combination of doping Y2O3 and SPS method will produce fully dense AlON ceramics with improved performance at relatively low temperature (1600 °C). It is notable that Y2O3 concentration shall be about 0.6 wt%. SPS of AlON doped with Y2O3 is a rate controlled sintering.