Abstract: Fly ash-based cordierite ceramics samples were prepared with fly ash, talc, alumina and magnesium oxide, by adding yttrium fluoride (YF₃) with mass fraction of 0%, 0.5% and 1.0%, respectively. The effect of YF₃ on phase composition, microstructure and physical properties of samples were studied. The results show that the introduction of YF₃ reduces formation temperature of cordierite, improves phase conversion rate of cordierite, significantly increases the mechanical properties and has a moderate positive effect on thermal properties of samples. When the YF₃ content is 0.5%, the performance of sample is the best. For the sample with 0.5% YF₃ content, when the sintering temperature is 1 300 ℃, no obvious peak corresponding to any impurity is found in XRD patterns, the bulk density of sample is 2.15 g·cm^-3, the open porosity is 7.49%, the water absorption is 3.49% and the compressive strength is 252.27 MPa. After 5 times heat shock experiments, the compressive strength is still high to 204.65 MPa. The heat capacity is 0.770~0.931 J/(g·℃) (25~150 ℃), and thermal expansion coefficient is 2.54×10^-6 ℃^-1 (100~800 ℃). The bulk density of sample with 0.5% YF₃ content increases by 5.2%, open porosity decreases by 58.6%, water absorption decreases by 60.6%, compressive strength increases by 4.6 times, heat capacity increases and the thermal expansion coefficient decreases, compared with the sample without additives.In the sintering process of fly ash-based cordierite ceramics, the introduction of YF₃ can form a liquid phase at a lower temperature, improve the mobility of elements, and promote the development of grains and fine grain size. As an effective sintering additive, YF₃ significantly improves the comprehensive properties of fly ash-based cordierite ceramics with a small content. This work broadens the additives range for high quality ceramic materials, which provides reference for excellent materials sintered at high temperature.

Key words: fly ash, cordierite ceramics, yttrium fluoride, compressive strength, heat shock resistance, heat capacity, thermal expansion coefficient