Thermal shock resistance of α/β-sialon ceramic composites

The thermal shock properties of α/β-sialon composites have been evaluated with an indentation-quench method based on propagation of Vickers cracks. Nominally the z value of the β-phase (Si6-zAlzOzN8-z) was held constant at 0.6, and the composition of the α-sialon phase YxSi12-(m+n)Alm+nOnN16-n was x=0.33, m=1.0, n=1.2. Different α/(α+β) ratios were tested, and the amount of sintering aid (a yttrium-containing glass phase) was varied between 0 and 20 vol.%. The thermal shock resistance increases with increasing fraction of β-phase, and the presence of a glass phase also has a positive influence on the thermal shock resistance.