The creep and static fatigue of Sialon ceramics with different grain size and fracture toughness were investigated. The grain size was controlled by using two kinds of starting raw materials. One consisted of β -sialon powders mainly, and the other, α -Si3N4 powder mainly. The sintered sialon using β -sialon powders had small grains and low Kc. On the other hand, samples using α -Si3N4 mainly had large grains and high Kc. There was no difference in the creep properties at 1350°C dependent on the grain size. The estimated creep exponent were 1.7-1.9. The crystallization of the grain boundary glass phase to Yb3Al5O12 decreased the strain in primary creep, and inhibited the rupture in short time.
