Thermal shock fracture test using an infrared radiation heating (IRH) method was performed on alumina and two kinds of silicon nitride that have high and normal thermal conductivity. The thermal shock strength, R1c, and thermal shock fracture toughness, R2c, of these materials were estimated experimentally and theoretically, where the experimentally obtained values, which were termed experimental R1c or R2c, were measured by the IRH technique, and the theoretical values were calculated using material properties, which were termed calculated R1c or R2c. The results revealed that the silicon nitride having high thermal conductivity showed three-fold higher R2c value than the silicon nitride with normal thermal conductivity. A technique for estimating the R1c value using the experimental R2c was also developed, because it is difficult to measure the thermal shock strength, R1c, for materials with high thermal shock resistance, using the IRH technique, due to insufficient heat flux.
