<p>Ceramic thin plates were prepared using kaolin, potassium sodium feldspar and quartz powder as the main raw materials and kaolin, <i>α</i>-Al₂O₃, MoO₃ and AlF₃·3H₂O as additives. The experiment examined the effects of different additives on mullite formation, as well as the microstructure and properties of the ceramic thin plates. Additionally, the study explored the toughening and strengthening mechanisms induced by the additives, providing a theoretical foundation for further optimizing the toughness of ceramic thin plates. The results showed that the D4 sample fired at 1 220 °C (with an addition of 20 wt% <i>α</i>-Al₂O₃) exhibited the best performance, with a water absorption rate of 0.07%, apparent porosity of 0.18%, bulk density of 2.75 g· cm⁻³, firing shrinkage of 12.76%, bending strength reaching 101.93 MPa, and fracture toughness of 2.51 MPa·m^1/2. As the amount of <i>α</i>-Al₂O₃ additive increased, the ceramic thin plates exhibited a greater abundance of short rod-like mullite and corundum grains, which were tightly packed together, forming a framework for the ceramic thin plates. This microstructure enhanced pathways for crack propagation, dispersed internal stresses, and increased fracture surface energy, resulting in significant improvements in both strength and fracture toughness of the ceramic thin plates.</p>