Effect of ZrO2 addition on the structure and the crystallization delay in lithium disilicate based glasses

Lithium disilicate (LD) glasses in system (99-X)(1Li2O:2SiO2)-(1K2O)-XZrO2 (X = 0, 1 and 2 mol %) have been synthesized by melt quenching technique and converted into glass-ceramics by three and four-stage heat treat-ment schedules. The sequence of phase formation in glass-ceramics with ZrO2 addition has been discussed. The activation energy of crystallization increases with the addition of ZrO2. Rietveld refinement and micro structural analysis show an increase in the amorphous content with the addition of ZrO2. 29Si MAS-NMR, Raman and XPS spectroscopy studies for the glasses reveal that the ZrO2 addition to LD based glasses causes network polymeri-zation and changes the role of network modifying Li thorn and K thorn species into charge compensators. The increased connectivity of [ZrO6]2-units in the glass network restricts the mobility of Q2 [Si2O6]4-, Q3 [Si4O10]4-and Q4 [SiO2] units, which leads to an increase in activation energies of crystallization and hampers the devitrification ability of glasses.