In this work, cordierite ceramics were prepared by using high-temperature solid-state reaction method, while fly ash, talc, alumina and magnesium oxide were used as raw materials and erbium oxide (Er₂O₃) was employed as dopant with mass contents of 0, 0.5% and 1.0%. The effects of erbium oxide on phase composition, microstructure and physical properties of the cordierite ceramics were studied. Firstly, the doping of Er₂O₃ promoted the phase formation of cordierite. The optimal doping content is 0.5 wt.% Er₂O₃. The conversion efficiency of cordierite was increased by forming a liquid phase at low temperatures, thus leading increase in the migration rates of Mg²⁺ and Al³⁺. Secondly, with 0.5 wt.% Er₂O₃, after sintering at 1300 ℃, the specimens had single phases, complete crystallization, suitable grain orientation and absence of abnormal grain growth. Lastly, the optimized sample had bulk density of 2.095 g·cm^-3, with the apparent porosity and water absorption rate to be 14.86% and 7.09%, respectively. Meanwhile, the compressive strength was 149 MPa, which was 230% higher than that of the undoped specimen. It is confirmed that Er₂O₃ is a promising sintering aid to significantly improve the comprehensive performance of cordierite ceramics.

In order to overcome the mechanical weakness of cordierite ceramics based on fly ash, lanthanum fluoride (LaF₃) was introduced in the fabrication process as high efficiency additive, resulting in cordierite ceramics with excellent mechanical properties. When the addition of LaF₃ was 1.0 wt.% and the sintering temperature was 1300 ℃, elastic modulus, hardness and compressive strength of the samples were 200.09 GPa, 17.63 GPa and 118.41 MPa, respectively. The significant enhancement was mainly attributed to the enhanced liquid fluidity and densification effect. At the same time, lanthanum was enriched at grain boundaries to facilitate grain refinement and toughening. Besides, a small quantity of lanthanum might be incoporated into the cordierite lattice, which would have a positive effect on mechanical strengthening.