The Effect of the MgO/Al₂O₃ Ratio on the Thermal and Refractory Behaviors of Cordierite Ceramics

In this study, cordierite-based ceramics (2MgO·2Al₂O₃·5SiO₂) were synthesized using high-purity MgO, Al₂O₃, and SiO₂ as starting materials. The influence of the MgO/Al₂O₃ ratio on various properties, including the thermal behavior, pyrometric cone refractory behavior, phase formation, physical properties, and microstructure of the synthesized ceramics, was systematically analyzed. Increasing the MgO/Al₂O₃ ratio progressively weakened the cordierite network, leading to lower temperatures for liquid formation and melting. This resulted in reduced viscosity and increased fluidity. Subsequently, the thermal and refractory behaviors were observed at lower temperatures with higher deformation rates under higher MgO/Al₂O₃ ratios. The lower viscosity of the liquid formed at reduced temperatures contributed to an increase in the density of sintered bodies, reduced porosity, and enhanced shrinkage. X-ray diffraction analysis confirmed that cordierite was the predominant phase in samples sintered at 1300, 1350, and 1400 °C, with higher cordierite formation at higher temperatures. Conversely, the formation of secondary phases, such as spinel, cristobalite, and enstatite, decreased with increasing sintering temperature. Pyrometric cones were then constructed for a range of temperature settings, and their deformation characteristics at specific temperatures were used to evaluate the refractoriness under diverse conditions.