A new strengthening theory for improving the fracture strength of lithium disilicate glass-ceramics by introducing Rb or Cs ions

The lithium disilicate (LD) glass-ceramics with the SiO2-Li2O-R2O-Al2O3-P2O5-CeO2 system were prepared by adding R2O (R = K, Rb, Cs) as modifier. The effects of R2O addition on the crystallization behavior, microstructure and fracture strength of the LD glass-ceramics were investigated by differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM) etc. The results indicate that the fracture strength of LD glass-ceramics could be improved greatly by introducing Rb2O or Cs2O instead of K2O, therein, introducing Rb2O instead of K2O improved the fracture strength by 26% and Cs2O substituting K2O improved the fracture strength by 37%. The crystallization activation energy of different crystal phase was calculated. It was found that the lower the crystallization activation energy of lithium disilicate is, the higher the fracture strength of LD glass-ceramic achieves. Based on the results, a new chemical strengthening theory of LD glass-ceramic has been proposed, which is of great significance for developing LD dental restorative materials and other functional glasses.