An infrared radiation heating method was proposed previously as anew t
echnique for estimating thermal shock strength and thermal shock fract
ure toughness of ceramics using a thin-circular disk with or without a
n edge crack, heated by infrared rays at the center with a constant he
at flux. In this paper, thermal shock fracture toughness was measured
by the above method in four kinds of silicon nitride. Temperature dist
ributions, thermal stresses and stress intensity factors for the speci
mens were also analyzed considering the temperature dependent thermal
conductivity, thermal diffusivity and thermal expansion of the materia
ls. The experimental results show that the highest value of thermal sh
ock fracture toughness was observed in the material having the higher
thermal conductivity, which was developed by growing the grains and de
creasing the amount of the grain boundary phase.