Effects of nucleation agent particle size on properties, crystallisation and microstructure of glass-ceramics in TiO ₂ -ZrO ₂ -Li ₂ O-CaO- Al ₂ O ₃ -SiO ₂ system

The objective of this study was to evaluate the effects of P2O5 particle size distribution on the crystalline phases and microstructure of lithium disilicate glass-ceramics derived from the TiO2-ZrO2-Li2O-CaO-Al2O3-SiO2 system for dentistry applications. The samples were made via fusion and casting procedure. Crystallisation as well as the morphology and microstructure of the samples were investigated using X-ray diffraction, differential scanning calorimetric and scanning electron microscopy. The results showed that the crystallisation of the samples occurred in the range of 500-650°C. The main crystalline phase was lithium disilicate (Li2Si2O5) along with Lithium metasilicate (Li2SiO3), spodumene [LiAl(SiO3)2], lithium orthophosphate (Li3PO4) and cristobalite as secondary phases. With decreasing size of P2O5 particles, the morphology of Li2Si2O5 crystals was transformed from needle shaped to spherical-like and the mechanical property was improved. The optimal flexural strength of 280 MPa and microhardness of 620 HV were obtained at the lithium disilicate glass-ceramics with P2O5 nanoparticles.