A threshold heating rate for single‐stage heat treatments in glass‐ceramics containing seed formers

Abstract

AbstractThe development of glass‐ceramic materials is often achieved using an elementary microstructural strategy that splits the tasks of seed formation and functionality between two types of crystals. This strategy requires customized time‐temperature ceramization protocols, which have been so far implemented using empirical parameters. Here, a more fundamental approach is proposed: the extent of overlap Oe between seed formation and volume crystallization is evaluated by calorimetric and dilatometric measurements, targeting the computation of a threshold heating rate qt for effective single‐stage heat treatments. The applicability of this novel parameter is tested in TiO2‐doped lithium magnesium aluminosilicate glass‐ceramics, whose seed formation stage is thoroughly characterized by Raman spectroscopy and STEM. High‐temperature X‐ray diffraction demonstrates that insufficient seeding results in potentially weaker performances of the final products, due to large sizes and silica deficiency of the functional quartz solid solution crystals.