Nucleation and growth kinetics and phase analysis in zirconia-containing lithium disilicate glass

Stoichiometric lithium disilicate glass was doped with up to 5 mol% ZrO2. The zirconia addition leads to higher viscosities and additionally to a change in the crystallization behavior. The glass transition temperatures and the onset of crystallization are shifted to higher temperatures. While in the undoped sample and the glass containing 1 mol% ZrO2, lithium disilicate is the sole crystal phase, in the glasses with higher zirconia concentrations, lithium metasilicate, quartz, and ZrO2 precipitate. Furthermore, with increasing zirconia concentration, the volume nucleation rates are remarkably decreased and the induction times of nucleation are increased. For zirconia concentrations > 2 mol%, volume nucleation was not observed even after long heat treatment times; instead, surface crystallization solely occurred. This cannot be explained only by the higher viscosities of the ZrO2-containing glass. Hence, zirconia acts as nucleation inhibitor for volume nucleation in stoichiometric lithium disilicate glass.