<p>Cordierite-mullite kiln furniture for lepidolite calcination was prepared from cordierite, M45 mullite, and clay with the addition of potassium feldspar fines. The effects of potassium feldspar content and firing temperature on phase composition, microstructure, mechanical properties, and thermal shock resistance were investigated. The findings indicate that the incorporation of potassium feldspar enhances the liquid phase content in the samples without significantly altering the phase compositions, thereby facilitating the densification of the materials. In combination with the thermodynamic calculations and the results of the finite element simulation, it is evident that the stresses within the cordierite-mullite system result in less damage to the samples and exhibit a lower degree of stress concentration in the aggregate compared to the mullite-cordierite system. The porous structure of the cordierite aggregate, combined with stress concentration, leads to the formation of microscopic cracks that redirect crack propagation and consume additional fracture energy as the cracks extend. Consequently, cordierite-mullite kiln furniture exhibits a fracture strength of 16.5&#xa0;MPa and a retention rate of 92.7% following thermal shock.</p>