Effect of temperature and magnesia on phase transformation kinetics in stoichiometric and non-stoichiometric cordierite ceramics prepared from kaolinite precursors

The influence of temperature and magnesia content on the formation of phases and their transformation kinetics in stoichiometric and non-stoichiometric cordierite ceramics prepared from Algerian kaolinite precursors was investigated. High-temperature X-ray diffraction was used to study the formation of phases and their transformations. Non-isothermal differential thermal analysis was used to determine kinetic parameters for the formation of μ and α cordierite. Activation energies were calculated by Kissinger, Boswell, and Ozawa equations. The Augis–Bennett and Matusita equations were used to calculate the mode of crystallization (n) and dimension of growth (m) parameters, respectively. The synthesized materials showed similar phase transformations, which finally led to the formation of cordierite in stoichiometric kaolinite–magnesia mixture, and cordierite along with other phases in kaolinite–magnesia mixture containing excess magnesia. The activation energy for the formation of α cordierite was higher than that of μ cordierite. Energies of formation of μ and α cordierite phases in the non-stoichiometric samples were higher than those in the stoichiometric sample. The activation energy was less sensitive to the calculation method; however, it changed significantly with MgO content. Activation energies between 573 and 964 kJ mol⁻¹ were obtained. Magnesia changed the crystallization mode and crystal growth dimension. The kinetic parameters n and m, for the formation of μ or α cordierite, had values between 2 and 3.