Cordierite, Mg₂Al₄Si₅O₁₈, has a very low thermal expansion coefficient, thus a high resistance to thermal shocks. Accordingly, it is used in applications where high resistances to thermal shock, as well as chemical stability at high temperatures are essential; such is the case of Diesel particulate filters (DPF). This paper concerns the synthesis of cordierite by using the sol-gel method starting from two silicon-rich precursors: hydrophil aerosil and TEOS. When starting with TEOS, a magnesium carbonate basic pentahydrate  and aluminium nitrate, a monomineralic powder consisting of cordierite is obtained at temperatures lower than 1000˚C. In order to obtain corresponding ceramics, these powders were sintered at temperatures in the 1000–1350˚C range. The thermal expansion coefficient decreased with firing temperature increase. The ceramics fired at 1300˚C were submitted to chemical attack by an alkaline mixture (one mole Na₂CO₃ with 1.5 moles SiO₂) under so-called “less-severe” conditions, i.e., 900˚C and then under “severe” conditions at 1000˚C for 5 minutes. The SEM images evidence no corrosion in the first case, and slight corrosion features under the circumstance of the “severe” attack.