The effect of pre-existing crystals on the crystallization kinetics of a soda-lime-silica glass. The courtyard phenomenon

New data are presented on bulk crystallization in a glass of composition close to the stoichiometric phase Na2O . 2CaO . 3SiO(2). The effects of pre-existing crystals on the nucleation and growth behavior of secondary crystals are described for the first time. Primary crystals, grown at high temperatures, dramatically hinder the formation of new crystals at lower temperatures, in their vicinity (the courtyard effect). The crystal growth velocity decreases with increasing crystal size. Chemical analyses by energy-dispersive X-ray spectroscopy demonstrate that the above-mentioned effects result mainly from compositional changes of the glass matrix, in the neighborhood of the primary crystals, (C) 1999 Elsevier Science B.V. All rights reserved.