HIGH TOUGHNESS HIGH STRENGTH SIALONS CERAMICS.
Silicon Nitride and SiAlONs are the materials possessing unique combination of fracture toughness, hardness and strength and have potentials to be used in many industries.
A strive to further increase the reliability of these ceramics led to the use of many sintering aids and densification methods involving pressure and elongated pressureless sintering.
The problem associated with the fabrication of these ceramics has been how to impart high fracture toughness and, at the same time, retain high hardness and strength.
The key microstructural feature which controls the strength and toughness of SiAlON ceramics is the α→β phase transformation which takes place during densification at high temperature.
This transformation is accompanied by a growth of elongated β phase at the expense of equiaxed α-phase, as shown in Fig. 1 below.