Crystallization sequence within the keatite solid solution – cordierite mixed compositional triangle with TiO2 as nucleating agent

Abstract Sixteen glasses of mixed keatite solid solution – cordierite stoichiometry, with 4 mol% TiO2 as nucleating agent, were produced and ceramized to investigate their crystallization sequence. Employed analytical methods included differential scanning calorimetry, X-ray diffraction and scanning electron microscopy. Differences were identified already during the first ceramization stages: Al2O3/(Al2O3 + SiO2) and Li2O/(Li2O + MgO) ratios were crucial to determine which seed former phases would precipitate and the nucleation efficiency of each glass, reaching its maximum at Mg-free composition. Metastable formation of high quartz solid solution was observed in all samples; this phase was most persistent at Li2O/(Li2O + MgO) ratio equal to 0.33 and high SiO2-enrichment. Its destabilization led to the appearance of keatite solid solution and/or indialite, whose crystallization sequence and final relative amounts, as well as the microstructure of the glass-ceramics, were strongly influenced by the composition of the parent glasses.