Crystallization and SiAl ordering in cordierite glass-ceramics

Abstract Glass samples of cordierite composition Mg 2 Al 4 Si 5 O 18 , increasingly doped with TiO 2 as nucleating agent, were ceramized up to 1300 °C and analyzed to highlight differences in their crystalline evolution. Employed analytical methods included HT-XRD, DSC and Raman spectroscopy. Glass-ceramics displayed a gradual transition to effective bulk crystallization with increasing TiO 2 -doping, manifested by earlier and sharper formation of MgO-Al 2 O 3 -SiO 2 solid solutions of high-quartz structure. The further phase transformation into indialite equally appeared to be influenced by TiO 2 -content and to be closely related to the compositional and structural evolution of the seed formers, Mg-Al-titanate and rutile. Furthermore, the indialite-cordierite ordering process was investigated by computation of the ordering index at various temperatures from XRD and Raman, again revealing marked differences between TiO 2 -free and TiO 2 -bearing compositions.