Evaluation of Thermal Shock Resistance for Ceramic Materials by Young’s Modulus

When a sudden temperature difference is applied to a brittle material such as ceramics, some cracks will occur in the material and it may fracture in some case. The generated cracks as a fracture origin may cause the strength reduction, so the evaluation of thermal shock resistance is very important for ceramic materials. In the conventional evaluation of the thermal shock resistance (thermal shock fracture temperature, ΔTC), the fracture stress is measured after thermal shock test as a function of temperature difference. For this method, however, many specimens are required to estimate fracture stress by bending test and the variation of the stress is large. In the present study, we tried to specify the temperature of crack initiation by measuring Young's modulus and fracture stress before and after a thermal shock test with different temperature difference. Polycrystalline alumina with high purity was used for evaluation of thermal shock resistance. The Young's modulus of all specimens was measured by resonance method. The specimen at the prescribed temperature between 200°C and 600°C, it was quickly put into water to apply thermal shock. The Young's modulus of specimens after the test was measured and the change in Young's modulus before and after thermal shock test was evaluated. Further, the specimen after the evaluation was measured the fracture strength. As a result, it was found that Young's modulus is possible to estimate thermal shock resistance. Further it is also possible to evaluate thermal shock behaviors using only one specimen.