Abstract <p>Known for its near-zero coefficient of thermal expansion (CTE), cordierite demonstrates to be beneficial for many applications, but it is hard to be synthesized without the high CTE of impurities. In the study, pure cordierite powders were successfully synthesized via a non-hydrolytic sol-gel (NHSG) route with microwave assistance. The gelation process and phase transformation after calcination were carefully investigated. The analysis revealed that the main impurities generated during the synthesis were tridymite and spinel, both of them vanished after calcining at 1300 °C. Meanwhile, based on the deep characterization of the cordierite crystal, it also exhibited phase transformations from <i>μ</i>-cordierite to <i>α</i>-cordierite and finally to <i>β</i>-cordierite. The final product consisted of <i>β</i>-cordierite with a minor <i>α</i>-cordierite fraction. We expected that this study would not only provide an efficient approach to synthesize or dope ions in pure cordierite powders, but also reveal the mechanism of the cordierite’s phase transformations in detail.</p> Graphical abstract <p></p>