Controlled precipitation of lithium disilicate (Li2Si2O5) and lithium niobate (LiNbO3) or lithium tantalate (LiTaO3) in glass-ceramics

In the present study, the crystallization principles and phenomena of base glasses from the system of SiO2-Li2O-P2O5-Al2O3-K2O-Nb2O5 or Ta2O5 were investigated. Annealing parameters such as temperature and time were varied. Annealing the base glasses 10 min at temperatures < 850 degrees C for Nb2O5 or Ta2O5 containing samples lead to the crystallization of Li2SiO3. At higher annealing temperatures or longer annealing times, Li2SiO3 disappeared and Li2Si2O5 was the main crystal phase in all glass-ceramics. After the dissolution of Li2SiO3, the minor crystal phases of LiNbO3 or LiTaO3 were precipitated. Increasing the annealing temperatures as well as the annealing times lead to higher bending strengths up to about 676 MPa and CR-values of up to 100. Increasing the contents of Nb2O5 or Ta2O5 lead to higher CR-values. The radiopacities increased up to 355% compared to aluminum.