Thermal shock resistance of Si3N4 and Si3N4–SiC ceramics with rare-earth oxide sintering additives

The influence of various rare-earth oxide additives and the addition of SiC nanoparticles on the thermal shock resistance of the Si3N4 based materials was investigated. The location of SiC particles inside the Si3N4 grains contributed to a higher level of residual stresses, which caused a failure at the lower temperature difference compared to the composites with a preferential location of the SiC at the grain boundaries. A critical temperature difference increased with an increasing ionic radius of RE3+ for both the composites and the monoliths. The critical temperature difference for the composite (580 °C) and the monolith (680 °C) sintered with La2O3 was significantly higher compared to the composite and the monolith doped with Lu2O3 (430 °C). A good agreement was found between the results of the critical temperature difference estimated by the indentation quench test and that obtained by the strength retention method.