Effect of [SiO₂]/[Li₂O] on the microstructure and properties of lithium disilicate glass-ceramics containing lithium tantalate as a secondary phase

Our previous work proposed a phase reaction equation for the current lithium disilicate (LD) glass-ceramic system containing lithium tantalate (LT) as a secondary phase: 2(Li₂SiO₃) + Ta₂O₅ → Li₂Si₂O₅ + 2(LiTaO₃). The present study had a goal of finding support for the proposed equation by examining the effect of the ratio of [SiO₂] to [Li₂O] on the phase assemblage and microstructure of this system. The study also examined the microstructural effects on several properties of this system. A 15-sample data set was created by designing three microstructures for each of the five compositions. It was found that the LT/LD ratio from X-ray diffraction peak counts, as well as from Rietveld refinement, increased in the material as [SiO₂]/[Li₂O] decreased, supporting the proposed reaction equation. As [SiO₂]/[Li₂O] decreased, bulk density and CTE increased, while L* (lightness vs darkness) and Knoop hardness values decreased. The microstructure had little effect on radiopacity, but the addition of extra Ta₂O₅ into the composition lead to increased radiopacity values.