Influence of Y2O3 on densification, flexural strength and heat shock resistance of cordierite-based composite ceramics

In order to fabricate a heat transfer ceramic-based pipeline for concentrated solar power, rare earth Y2O3 was utilized as a modifying agent to improve the physico-chemistry properties of the cordierite-based composite ceramics. The influences of the sintering temperature and Y2O3 additive on the densification, flexural strength, and thermostability were investigated. The research results indicate that the densification degree of the composite ceramics gradually increases with elevated temperature, and the initial sintering temperature decreases with the addition of Y2O3. In addition, the flexural strength and heat shock resistance of the ceramic materials were improved with the addition of Y2O3. In particular, a sample containing 7 wt% Y2O3 (sample E4) sintered at 1360 degrees C showed the best properties with a relative density of 92.49%, a flexural strength of 126.81 MPa, and strength loss rate of -7.74% after 30 heat shock cycles. X-ray diffraction and scanning electron microscopy analysis showed that parts of Y3+ ions dissolving into high-temperature liquid phases could reduce liquid viscosity to accelerate grain crystallization and pore elimination. The second phase of yttrium silicate properly impeded the generation of beta-spodumene with lower strength during the heat shock process. Overall, a cordieritebased composite ceramic with low porosity was obtained with high mechanical strength and heat shock resistance and can be regarded as a highly potential material for solar heat transfer pipelines.