Microstructure evolution and thermal shock behaviour of iron-doped mullite-corundum ceramics

Mullite-corundum ceramics with various mullite crystal structures were prepared by incorporating Fe 2 O 3 into the ceramic powder. The impact of the Fe 2 O 3 content on the morphological evolution and formation mechanism of mullite crystals, as well as the thermal shock resistance and enhancement mechanism of the ceramic, were investigated. The results show that Fe 2 O 3 facilitates the formation of a low-viscosity liquid phase and enhances the dissolution-precipitation mass transfer rate at the liquid/solid interface, forming an iron-containing mullite solid solution, inducing lattice distortion, and accelerating the c-axis growth of mullite crystals. With increasing Fe 2 O 3 content, the mullite crystals changed from short columnar to elongated structures, and the grains were gradually interwoven with each other to form a network structure. The intergranular fracture mode of the sample was transformed into a mixed mode of transgranular and intergranular fractures. The maximum flexural strength was 83.60   MPa, with a retention rate of 94.65%, indicating improved strength and thermal shock stability.