Effect of Al/Si ratio on crystallization of cordierite ceramics prepared by the sol-gel method

The application of cordierite ceramics as the electronic materials has recently extended immensely, because of their superior heat resistance, low dielectric constants, etc. In this study, the cordierite ceramics, which can be sintered at low temperature without any nucleation agents, were prepared by the sol-gel method. The effect of Al/Si ratio on the crystallization behavior and sintering was investigated. Metal alkoxides, Si(OC₂H₅)₄, Al(OC₄H₉s)₃, and Mg (OC₂H₅)₂ were hydrolyzed in 2-methoxyethanol, resulting in gelation. The obtained gel powders were heat-treated at various temperatures. As the Al/Si ratio decreased, the deposition of μ-cordierite occurred at lower temperatures. The initial transformation of α-cordierite phase from μ-cordierite phase took place by heat treating at 950°C for 1h. However, the complete transformation to single α-cordierite phase was retarded and achieved at higher temperatures, >1050°C. With the increase of Al/Si ratio, the initial transformation to α-cordierite from μ-cordierite occurred at higher temperatures, while the complete transformation took place rapidly at lower temperatures, about 1000°C.